Distortion mitigation in directed energy deposition

Abstract

This application provides a bending clamping die and a system and method for manufacturing objects (particularly titanium and titanium alloy objects) using the bending clamping die via directional energy deposition. The method includes thermally pre-bending a substrate on which the object to be manufactured is placed to form a pre-bent substrate, attaching the pre-bent substrate to a fixture using the bending clamping die as a lower support, preheating the substrate, and forming the object on the preheated pre-bent substrate using directional energy deposition technology.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for mitigating distortion in metallic objects manufactured using a directional energy deposition additive manufacturing process, also known as solid freeform manufacturing, particularly in titanium and titanium alloy objects. Background Technology

[0002] Structural metal parts, such as those made of titanium or titanium alloys, are manufactured from solid blanks using conventional methods such as casting, forging, or machining. The disadvantages of these techniques are significant material waste from the expensive titanium metal, which is typically machined away, and long lead times associated with the manufacture of the metal parts.

[0003] Fully dense physical objects can be manufactured using techniques known as directed energy deposition (DED), rapid prototyping, rapid manufacturing, layered manufacturing, additive manufacturing, shaped metal deposition, or additive manufacturing. DED of metals is an additive manufacturing process where focused thermal energy is used to fuse materials by melting them as they are deposited. Additive manufacturing offers significant manufacturing freedom and potential cost savings due to the layered stacking of near-net-shape products. It is also desirable to match the material properties of conventional monolithic forming processes (such as forging) while utilizing the same established metal alloys. DED is used for repair, rapid prototyping, and the manufacture of low / high volume parts.

[0004] DED systems comprise various types of machines that utilize one or a combination of DED energy sources, such as laser beams (LB), electron beams (EB), or arc-based energy sources like plasma arcs (PA), gas tungsten arcs (GTA), and gas metal arcs (GMA). The metallic feedstock used in DED systems typically comprises metals in powder and / or wire form. DED is usually performed in an inert gas atmosphere (e.g., using arc-based or LB-based DED systems) or in a vacuum atmosphere (EB systems). While these are the primary methods used in practice, other energy sources, feedstocks, and atmospheres can be used in any combination.

[0005] Residual stress can be defined as the self-balancing stress that exists in an elastomer even in the absence of external loads (e.g., thermal and / or mechanical loads). Due to localized heating and cooling cycles, significant amounts of weld-induced residual stress may arise and accumulate during the die-casting (DED) of a metal preform as the heat source melts the metal material, deposits each new metal layer, and remelts previously solidified metal layers. The incompatible elastic and / or plastic strain fields involved in the DED of metal, caused by non-uniform thermal loads near the processing area, inevitably lead to the accumulation of complex thermally induced residual stresses and distortions during the lamination process. Thermal expansion and contraction can occur as a result of transient thermal shifts and steep thermal gradients that may be present during DED. The formation and relaxation of residual stresses during the DED of metal can cause unwanted plastic deformations in areas bordering the processing area, which can persist into the deposited preform. Residual stresses locked in the deposited DED preform can lead to permanent loss of tolerances in the workpiece because the workpiece self-balances with the residual stress field still present in the structure upon release from the clamping platform or fixture. Deformation caused by residual stress is more significant for larger components due to the coexistence of larger temperature differences along the DED deposition process. Unfavorable distribution of residual stress in engineered components can also lead to unexpected or premature failure, i.e., in areas of high tensile stress that are prone to fracture and fatigue. Stress-relieving heat treatment is typically used to eliminate stresses that remain locked in the deposited preform due to the DED manufacturing sequence. However, tolerance losses remain one of the main concerns in most DED processes.

[0006] Residual stresses during metal deposition (DED) are typically caused by the fact that different regions of the manufactured part undergo varying cycles of thermal expansion and contraction. The resulting thermal stresses can lead to a non-uniform distribution of irreversible material deformation, some of which can remain after cooling, creating an internal and completely self-balancing stress field within the workpiece. This self-balancing can cause the metal structure to geometrically exceed tolerances due to distortion or warping. All forms of DED involve significant localized heat transfer to the top of the newly deposited layer (exposed to a heat source), the interface between the newly deposited layer and the previous layer, and / or the substrate at the interface used to achieve proper fusion.

[0007] Typically, a heat source with a high heat concentration is used in DED manufacturing processes to generate rapid heating. The resulting heat causes thermal expansion of the material, accompanied by a gradual decrease in yield strength. The heat generated by the heat source is used to melt powder and / or wire raw materials and create a weld pool in a portion of the workpiece. This locally applied energy causes the weld area to heat rapidly relative to the surrounding area, which remains at a relatively low temperature, resulting in localized fusion. Because the molten material will not support the load, the stress below the heat source is close to zero. At a short distance from the energy application area, i.e., immediately adjacent to the molten pool and in the material in the underlying structural layer, the material expands due to heating but is constrained by the adjacent and lower, cooler material, resulting in elastic compressive strain. Therefore, the stress in the region adjacent to the heat source is compressive. Due to the high temperature and low yield strength of the material in the regions adjacent to the heat source, the stress in these regions can be as high as the yield strength of the material at the corresponding temperature. As the heat source moves away from the energy application area, the heated molten material cools and contracts as a solid, but the contracting metal is mechanically restrained by the adjacent and lower material layers. As cooling continues, the residual stress within the object is distributed, typically exhibiting large tensile stresses at the top layer to prevent material shrinkage and to balance the compressive stresses below. In some applications, the tensile stresses generated at the top layer can approach the yield strength of the material. To balance the compressive forces, if the distortion and compressive loads involved exceed the critical buckling load, buckling may occur in the metallic structural member.

[0008] Due to the layer-by-layer nature of the DED process, the difference in heating and cooling loads applied by each successive layer leads to spatial competition between material expansion and contraction, ultimately resulting in the accumulation of residual stress in the object being produced. Because the hot layer of molten metal is deposited on the previously cooler layer of the object being built, large thermal gradients and significant localized contractions can exist as heat from the heat source travels through the workpiece, introducing residual stresses caused by incompatible strain fields into the workpiece. The longitudinal and transverse contractions that occur during lamination curing can amplify the accumulation of residual stresses within the deposited preform. Stress can be a function of the material's tensile modulus, coefficient of thermal expansion, and percentage of contraction during cooling. If the stresses generated by these incompatible strains remain in the final object and are not released, the residual stresses can combine and react to generate internal forces that cause unwanted distortions in the object, such as bending, buckling, and rotation. Residual stresses that can form during conventional additive manufacturing processes are sometimes large enough to cause significant distortion, mismatch, tearing, or stress-induced cracking in the additively manufactured object (see [link to documentation]). Figures 1A to 1H ).

[0009] Methods for measuring or modeling stress induction in formed products are known in the prior art (e.g., see U.S. Patent 9,555,475 (Sidhu et al. (2017)); 9,950,476 (Nguyen et al. (2018))). Prior art developed to address these drawbacks has achieved limited success. For example, post-weld high-pressure mechanical rolling has been used to plastically deform the consolidated material prior to the formation of subsequent layers (e.g., see UK Patent Application GB2491472 (2012) by Colegrove et al.). Methods for mitigating stress in the fabrication of parts by adding layers have been taught, for example, in U.S. Patent Application Publication 2017 / 0326681 (Sidhu et al. (2015)). The process involves distorting the deposition of each metal layer during the process. In these processes, one or more impact treatment devices are used to hammer or strike common points on the workpiece to plastically deform at least a portion of the deposited layer after it has cooled. Each impact treatment device can strike the workpiece once or multiple times, and can strike at frequencies up to 20 Hz. Laser hammering has also been used to transfer residual compressive stress into the workpiece (see US Patent Application Publication US2014 / 0367894, Kramer et al. (2014)). These methods are not suitable for parts with complex shapes to relieve residual stress in areas that cannot be accessed by hammering or rolling tools. They also introduce added time and complexity to the workpiece and may be too expensive or impractical to use.

[0010] These methods also increase interlayer waiting time, which negatively impacts productivity and potentially limits manufacturing freedom. Excessive cooling between layer depositions also increases temperature differences between layers and further exacerbates residual stress development. For methods that physically process deposited layers, contamination from the process will also be a problem, as any contaminants in additive manufacturing can become trapped between the layers of the final product.

[0011] Therefore, there is a need in the art for an economical method of performing direct metal deposition (DED) at a metal deposition rate in an additive manufacturing system, which produces metal products with reduced or minimized residual stress or distortion, or both, compared to those achieved in conventional additive manufacturing processes. It is desirable to provide a DED process that reduces the occurrence of residual stress or cracking in DED-manufactured objects. It is also desirable to provide a DED process that reduces the occurrence of localized distortion in the manufactured object during the deposition of an additional metal layer. Summary of the Invention

[0012] Therefore, the embodiments provided herein relate to the production of workpieces with reduced or minimized residual stress or distortion, or both, using additive manufacturing processes that substantially avoid one or more problems caused by the limitations and disadvantages of related technologies. As included and broadly described, apparatus, systems, and methods are provided for reducing or minimizing residual stress or distortion, or both, during metal additive manufacturing to achieve products with improved material quality. Products manufactured using DED with these reduced residual stress or distortion exhibit increased strength, fatigue resistance, and durability. The provided apparatus, systems, and methods can increase the production volume and yield of DED-formed products and produce workpieces within specified tolerances.

[0013] Because the method presented herein reduces or eliminates residual stress or distortion, or both, it can be used to manufacture medium to large-sized (e.g., up to 3m) DED formed parts that cannot be easily produced using conventional additive manufacturing processes. Furthermore, by reducing or eliminating the large amounts of residual stress, distortion, or combinations thereof typically found in conventional DED metal structures, manufactured metal structures can be produced geometrically within tolerances and specifications.

[0014] Because residual stress and distortion are often considered key obstacles to the mainstream acceptance of DED technology for metals, especially in safety-critical applications, the apparatus, systems, and methods presented in this paper, which minimize residual stress or distortion, could open up new markets or lead to wider acceptance of DED-manufactured components. The apparatus, systems, and methods presented in this paper also enable effective control of residual stress and distortion in DED metal structures, allowing for improved material utilization efficiency for both the substrate and the DED material. These improvements in material utilization, combined with the production of DED products within tolerances, result in less waste and rework, which can significantly reduce DED manufacturing costs.

[0015] A method for manufacturing DEDs is provided, comprising pre-bending a metal substrate to form a plastically pre-bent substrate prior to DED of a single-sided metal structure. A method for manufacturing DEDs is also provided, comprising pre-bending a metal substrate to form a plastically pre-bent substrate, and preheating the pre-bent substrate prior to DED of the metal structure. An apparatus for manufacturing parts having reduced residual stress and distortion caused by DED is also provided. This apparatus can be used with a conventional DED energy supply source for melting metal powder and / or wire feedstock. The apparatus includes a bending clamping die as a lower support structure for plastically pre-bending the substrate. A system using a conventional DED energy supply source is also provided, which is modified using CAD-CAM program instructions that, upon execution, cause the DED process to follow the shape of the lower bending clamping die.

[0016] Methods for manufacturing DEDs are provided that minimize or prevent distortion in the manufactured products. This increases the efficiency of the manufacturing process, for example, by minimizing substrate waste and the amount of deposited material that must be used. In particular, because the highest thermally induced stress field can be introduced into the first deposited layer, and the distortion effect can be seen specifically in the substrate, the method presented herein saves the base material sacrificed or lost in conventional additive manufacturing processes. Compared to conventional methods, this method leads to improved material utilization efficiency for both the substrate and the DED material. The method presented herein provides effective control over residual stress and distortion in the DED structure. This leads to reduced material waste, allowing the buy-fly ratio or BTF ratio to be nearly uniform. Reducing material waste and minimizing or eliminating rework time significantly reduces manufacturing costs.

[0017] A bending clamping die is provided. The bending clamping die includes: a first side comprising two or more cavities separated by one or more reinforcing members, and an edge having a flat surface surrounding a periphery of the first side; and a second side opposite the first side having a bent surface and including knurling or corrugation. The bending clamping die may include a ceramic coating. The reinforcing members may maintain die rigidity or provide resistance to die deformation, or both. The bending clamping die may include or be made of a non-magnetic metal. The bending clamping die may include or be made of a metal having a melting point of 1350°C or higher. The bending clamping die may include or be made of a metal that is or includes austenitic stainless steel. Austenitic stainless steel may include carbon, chromium, copper, manganese, molybdenum, nickel, nitrogen, phosphorus, silicon, or any combination of two or more of these. Austenitic stainless steel may include at least 18% chromium. Austenitic stainless steel may be a 300 series stainless steel. Austenitic stainless steel may include 304 stainless steel, 309 stainless steel, 310 stainless steel, 316 stainless steel, 318 stainless steel, 321 stainless steel or 330 stainless steel or combinations thereof.

[0018] A ceramic coating for a bending clamping die can be applied to any one or more surfaces. The ceramic coating may include zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, alkaline earth metal silicates, ZrV₂O₇, Mg₃(VO₄)₂, or combinations thereof. The ceramic coating may include ZrO₂·8Y₂O₃. The ceramic coating may have a thickness from 0.1 mm to approximately 5 mm. The bending clamping die may include a nominal die deflection of approximately 3 mm to approximately 35 mm. The bending clamping die may include an adhesive coating applied thereto to the ceramic coating. This adhesive coating may be between the surface of the bending clamping die and the ceramic coating.

[0019] Also provided is a directional energy deposition method for producing metal workpieces. The method may include pre-bending a substrate of metallic material using thermal energy to form multiple melting tracks on a first surface of a substrate by using a first melting tool; when the pre-bent substrate is secured to a fixture, a bending clamping die described herein is used as a lower support structure to support the pre-bent substrate, and multiple clamps are used to secure the pre-bent substrate and the bending clamping die supporting the pre-bent substrate to the fixture. After the pre-bent substrate and the bending clamping die are secured to the fixture, the method includes forming a metal workpiece on a second surface of the substrate by an additive manufacturing process, which may a) deposit a molten metal layer on the second surface of the substrate to form a base material, and deposit a subsequent molten metal layer on the base material to form the workpiece; or b) deposit a metal powder layer on the second surface of the substrate and melt the metal powder to form a base material, and deposit a subsequent metal powder layer on the base material and melt the powder to form the workpiece, wherein the second surface of the substrate is opposite to the first surface of the substrate. This method may include preheating a pre-bent substrate, fixed to a fixture, to a temperature of approximately 400°C to approximately 900°C by applying thermal energy to a second side of the substrate. The pre-bent substrate may include inducing a thermal gradient within the substrate. In this method, a melting tool may be used, comprising a heat source selected from laser beams, electron beams, plasma arcs, gas tungsten arcs, gas metal arcs, and any combination thereof. During pre-bending of the first surface of the substrate, the area of ​​thermal energy application may reach a temperature that is the melting point of the metallic material, or a temperature approximately 5°C to approximately 50°C less than or greater than the melting point of the metallic material. During pre-bending of the first surface of the substrate, the formation of melting tracks results in tensile stress at the centerline of each melting track as the substrate cools, and compressive stress in regions away from the centerline of each melting track. The tensile stress at the centerline of the melting track may be within approximately 10% of the yield strength of the substrate. The tensile stress at the centerline of the melting track may exceed the magnitude of the yield strength of the substrate.

[0020] The pre-bending step may include using a gas jetting device to direct cooling gas toward the melting trajectory to accelerate cooling of the melting trajectory. Directing the cooling gas toward the melting trajectory can create a thermal gradient in the substrate and can impart residual stress in the substrate upon cooling. The gas jetting device can direct the cooling gas toward the melting trajectory at a rate of approximately 50 L / min to approximately 500 L / min. The cooling gas can be applied at a constant flow, intermittently, or in a pulsed flow. The cooling gas may include an inert gas selected from argon, helium, neon, xenon, krypton, and combinations thereof. The cooling gas can be applied at a temperature of 100°C or lower. The cooling gas can be applied at a temperature of 25°C or lower. The gas jetting device can generate turbulence, laminar flow, or a combination of turbulence and laminar flow of the cooling gas. The gas jetting device may include multiple nozzles, and the nozzles can guide the cooling gas in a direction away from the heat source of the melting tool, and at least one nozzle can guide the cooling gas to the as-solidified metal of the melting trajectory.

[0021] In the method provided herein, melt tracks can be generated at equal intervals. The distance between melt tracks can be from approximately 10 mm to approximately 60 mm. The method may include determining the centerline of each wall of a preform to be formed on a second surface of the substrate; and positioning the melt tracks on a first surface of the substrate, approximately 10 mm to approximately 20 mm away from the centerlines of most of the walls of the preform or workpiece to be formed on the second surface of the substrate. Most of the melt lines may be formed at one or more locations on the first surface, rather than corresponding to locations occupying one or more areas by one or more walls of the workpiece to be formed on a second side of the substrate.

[0022] In this method, pre-bending can form a pre-bent substrate with uniform elastoplastic bending. Pre-bending of the substrate can be performed while the substrate is clamped to a fixture and thermally insulated from the fixture. Multiple clamps can be used to clamp the substrate to the fixture, wherein one or more clamps may include an insulating coating on each surface in contact with the pre-bent substrate. The insulating coating may include ceramic materials, silicon carbide, silicon nitride, boron carbide, or combinations thereof. Ceramic materials may include alumina, zirconium oxide, titanium oxide, alkaline earth metal silicates, aluminum titanate, zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, ZrV₂O₇, Mg₃(VO₄)₂, or combinations thereof. The thickness of the insulating coating may be from 0.1 mm to 5 mm. The clamps may include a knurled pattern or corrugations on the surface in contact with the pre-bent substrate. The clamps can be tightened to bring the pre-bent substrate into full contact with the underlying bending clamping die. Each clamp can be tightened to a torque of approximately 10 N·m to approximately 100 N·m. The clamps can be positioned such that they intersect at the beginning or end of the wall of the workpiece being produced.

[0023] In the method provided herein, preheating of the pre-bent substrate can be accomplished using one or more melting tools, each including a DED heat source, provided that a) a melting trajectory is formed but the surface of the pre-bent substrate is not melted; or b) a melting trajectory is formed and the surface of the pre-bent substrate is melted at the melting trajectory. The melting tool can be positioned at a distance greater than the distance between the workpiece and the pre-bent substrate.

[0024] The method may include preheating a pre-bent substrate comprising a first short edge and an opposing second short edge, and a first long edge and an opposing second long edge by means of the following steps: a) positioning a melting tool including a DED heat source at the first short edge and within approximately 10 mm to approximately 60 mm of the first long edge of the pre-bent substrate, which is fixed to a fixture; b) applying thermal energy from the DED heat source of the melting tool across the surface of the pre-bent substrate, beginning at the first short edge and across the surface of the second opposing short edge, to form a first energy line applied to the surface; c) repositioning the DED heat source of the melting tool to the first short edge and shifting it from the first energy application line toward the second long edge by a distance of approximately 10 mm to approximately 60 mm; and d) repeating steps b) and c) until the energy application line is applied across the surface of the pre-bent substrate to a position approximately 10 mm to approximately 60 mm from the second opposing long edge. Preheating may raise the temperature of the pre-bent substrate to approximately 350°C to approximately 650°C.

[0025] The formation of a metal workpiece may include providing a metal material in the form of a wire; using a single melting tool to heat and melt the metal material, causing the molten metal material to deposit onto a region of a substrate to form a base material; and moving the base material relative to the position of the melting tool in a predetermined pattern, causing the continuous deposit of molten metal material on the base material to solidify and form a three-dimensional object.

[0026] The formation of a metal workpiece may include a) providing a metal material in the form of a wire; b) heating at least a portion of the surface of a substrate using a first melting tool to form a preheated region on the substrate; c) heating and melting the metal material using a second melting tool, such that the molten metal material is deposited onto the preheated region to form a base material; d) moving the base material in a predetermined pattern relative to the positions of the first melting tool and the second melting tool; e) heating at least a portion of the surface of the base material using the first melting tool to form a preheated region on the base material, and depositing the molten metal material generated by melting the metal material using the second melting tool onto the preheated region on the base material; and f) repeating steps d) and e) such that the continuous deposit of molten metal material on the preheated region on the base material solidifies and forms a three-dimensional object.

[0027] The method may include using a gas jetting device to guide cooling gas to impact the surface of a solidified material adjacent to the liquid-solid boundary of the molten metal material, or any combination thereof; and moving the base material in a predetermined pattern relative to the positions of the melting tool and the gas jetting device, such that a continuous deposit of the molten metal material solidifies and forms a three-dimensional object. The first melting tool may include a PTA torch, a laser device, a coaxial powder feed nozzle laser system, an electron beam device, or any combination thereof, and the second melting tool may include a PTA torch, a laser device, a coaxial powder feed nozzle laser system, an electron beam device, or any combination thereof. The first melting tool may include a first PTA torch, and the second melting tool may include a second PTA torch. The first melting tool may include a laser device, and the second melting tool may include a PTA torch. The first melting tool may include a PTA torch, and the second melting tool may include a laser device. The first melting tool may include a coaxial powder feed nozzle laser system, and the second melting tool may include a laser device. The first melting tool may include a coaxial powder feed nozzle laser system, and the second melting tool may include a PTA torch. The first melting tool may include a PTA welding torch, and the second melting tool may include an electron beam device. The first melting tool may include an electron beam device, and the second melting tool may include a PTA welding torch. The first melting tool may include an electron beam device, and the second melting tool may include a laser device. The first melting tool may include a laser device, and the second melting tool may include an electron beam device. When the second melting tool includes a PTA welding torch, the PTA welding torch may be electrically connected to a DC power supply, such that the electrode of the PTA welding torch becomes a cathode, and the metallic material may be a consumable electrode that becomes an anode.

[0028] In the methods provided herein, each step of the methods for pre-bending the substrate, preheating the pre-bent substrate, and forming the metal workpiece can be performed in a closed chamber containing an inert atmosphere. The inert atmosphere may include argon, neon, xenon, krypton, helium, or combinations thereof.

[0029] Also provided is a system for directional energy deposition. The system may include a fixture for securing a pre-bent substrate; a bending clamping die, as described herein, positioned between the fixtures when the pre-bent substrate is secured to the fixture; an insulating clamp for securing the pre-bent substrate to the fixture; one or more melting tools including a DED heat source for melting a metal source into molten metal material deposited on the surface of a base material; a gas jetting device for directing cooling gas to impinge on solidified material at a liquid-solid boundary adjacent to the molten pool, or any combination thereof; a supply of cooling gas; and an actuator for positioning and moving the base material relative to the melting tools and the gas jetting device.

[0030] Additional features and advantages of the embodiments described herein will be set forth in the following description, will be apparent in part from the description, or may be learned by practice of the invention. The objects and other advantages of the exemplary embodiments will be realized and obtained through the structures particularly pointed out in the written description and its claims, as well as the accompanying drawings.

[0031] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative, and are intended to provide further explanation of the claimed invention. Attached Figure Description

[0032] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrating embodiments of the invention and serving, together with the description, to explain the principles of the invention.

[0033] In the attached diagram:

[0034] Figure 1A These are photos of workpieces produced using conventional DED additive manufacturing without stress relief. Figure 1B and Figure 1C The mismatch is shown (arrows point to the mismatch location). Figure 1D , Figure 1E and Figure 1F The image shows the workpiece cracking (arrow points to the crack). Figure 1G and Figure 1H The tear in the workpiece is shown (arrow points to the crack).

[0035] Figure 2A This is a side view of a bending clamping mold, showing an embodiment with a corrugated bent surface, wherein the ridge has a truncated cone shape as an exemplary cross-sectional shape, particularly a truncated pyramid shape. Figure 2B This is a side view of the same curved clamping die, showing the ceramic coating on the curved surface that will contact the DED substrate (plate) via dashed lines (enlarged in the figure). The figure also shows the nominal die deflection h. mold . Figure 2C An exemplary cross-sectional shape (enlarged view) is shown, which is truncated pyramidal, particularly truncated pyramidal.

[0036] Figure 3A This is a top view of the same bending clamping mold. Figure 3B These are equidistant projections of the same bending clamping mold.

[0037] Figure 4This is a bottom view of a bending clamping mold with four triangular cavities and peripheral edges, separated by X-shaped reinforcing members, wherein the peripheral edges and the X-shaped reinforcing members share a common plane. When the bending clamping member is placed on a fixture or welding table, only the peripheral edges and the reinforcing members contact the clamping fixing platform, such as the fixture or welding table.

[0038] Figure 5 An exemplary rapid cooling gas injection device is described.

[0039] Figure 6 The diagram shows the melt path generated on the first or rear side of the substrate for pre-bending the substrate, and the DED rear wall of the workpiece formed on the second or front side of the substrate.

[0040] Figure 7A An exemplary heating path is shown, which can be used to move the DED energy source to create a melting trajectory on the top surface of the back side or first side of the substrate in order to pre-bend the substrate toward the heat source.

[0041] Figure 7B The diagram schematically illustrates the relative position of the thermally induced pre-bending melt trajectory generated by the heating path on the rear or first side of the substrate with respect to the cover (gray dashed line) DED workpiece to be manufactured on the reverse front or second side of the substrate.

[0042] Figure 8A This illustrates the uniform longitudinal bending produced in the substrate when heated to induce a melt path and pre-bend the substrate. Figure 8B In the diagram, the substrate is flipped upside down. The maximum nominal substrate deflection 410 perpendicular to the plane of the plate in the depicted substrate is approximately 15 mm. In both figures, the pre-bent substrate rests on a fixture 400.

[0043] Figure 9A A bottom view of an exemplary insulated high-strength steel clip is shown. Figure 9B Its side view is shown. Figure 9C The figures show a tilted, top-down three-dimensional view. These figures depict exemplary surfaces that may be coated with a ceramic coating to minimize heat flow caused by conduction between the insulating high-strength steel clip and the pre-bent substrate when the clip is used to attach the plastic pre-bent substrate and the fixture.

[0044] Figure 10An exemplary clamping arrangement is shown, using insulating or corrugated clips to attach a pre-bent substrate to a fixture. The illustration shows that the clips can be positioned such that the centerline of the clip (or the clamping entity when several clips are used in combination, as shown in the solid frame outline surrounding the clips) intersects the centerline of the start / end position of the DED wall wherever possible. These substrate clamping constraints can substantially reduce the deformation effects caused primarily by longitudinal residual stress. Suboptimal clamping can lead to localized deformation or buckling due to a lack of clamping constraints. For illustration, a suboptimal clamping arrangement 650 is shown in the dashed box in the figure. Only one clip is used off-center to axially constrain the upward movement of the substrate. This is a suboptimal clamping arrangement because the centerline of the clip / entity does not intersect the centerline of the start / end position of the DED wall.

[0045] Figure 11 The diagram schematically illustrates the relative positions of the light black preheating path on the front side of the substrate prior to DED deposition, covering the shape of the workpiece to be formed. An exemplary embodiment illustrates the application of a low energy density applied by a heat source in the x-direction across the face of the pre-bent substrate in the y-direction, from short edge to short edge. The figure shows solid and light black dashed lines, representing, for example, the tool path and the preheating sequence of two parallel-traveling melting tools.

[0046] Figure 12A An example of a conventional directional energy deposition (DED) fabrication structure is schematically depicted, in which the substrate is separated from the fixture using, for example, an alumina insulating sheet or other substrate support mechanism, and the workpiece is fabricated in a stacked manner. This structure minimizes heat flow from the DED substrate to the fixture while preventing heat loss generated by the DED process.

[0047] Figure 12B An exemplary configuration for directional energy deposition using the bending clamping die provided herein is shown. The bending clamping die serves as a lower support structure for the pre-bent substrate when it is attached to the fixture. The bending clamping die has an insulating coating on top of the bent surface and thermally insulates the bending clamping die from the plastic pre-bent substrate. The workpiece is manufactured in a stacked manner.

[0048] Figure 13A The deformation caused by DED deposition is shown, which forms a workpiece on a first substrate with a thickness of 9.5 mm that has not been subjected to any type of stress relief. A noticeable distortion is observed at the short edge of the substrate, which bends upwards compared to the flat profile of the substrate before deposition. Figure 13B The deformation caused by DED deposition on a second substrate with a thickness of 12.7 mm is shown. This second substrate has not been subjected to any type of stress relief. Figure 13CA third substrate with a thickness of 9.5 mm is shown, which is used to form an object by being subjected to thermal pre-bending, preheating and DED treatment.

[0049] Figure 14A This is a diagram illustrating a suboptimal setup for a single clamp. Dashed circles represent areas of uneven pressure and heat transfer distribution. Figure 14B This is an illustration showing the setup of a single clip, which demonstrates a uniformly distributed load across the contact area between the clip and the substrate, thereby ensuring a uniform distribution of pressure and heat transfer. Detailed Implementation

[0050] Reference will now be made in detail to embodiments of the present invention, examples of which are shown in the accompanying drawings.

[0051] A. Definition

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise stated, all patents, patent applications, published applications and publications, websites and other publicly available materials mentioned throughout this disclosure are incorporated herein by reference in their entirety. In cases where terms herein have multiple definitions, the definitions provided in this section shall prevail.

[0053] As used in this article, the singular forms “one,” “a,” and “the” include plural references unless the context clearly indicates otherwise.

[0054] As used herein, ranges and quantities can be expressed as “approximately” a specific value or range. “Approximately” also includes exact quantities. Therefore, “approximately 5%” means approximately 5%, and also “5%”. “Approximately” refers to the expected application or purpose within typical experimental error.

[0055] As used herein, "optional" or "optionally" means that an event or condition, as described below, occurs or does not occur, and that description includes both the possibility that the event or condition occurs and the possibility that it does not occur. For example, an optional component in a system means that the component may or may not be present in the system.

[0056] As used in this article, “combination” refers to any association between two or more projects. This association can be spatial or indicates the use of two or more projects for a common purpose.

[0057] As used herein, the terms “comprising,” “including,” and “containing” are synonymous and are inclusive or open-ended. Each term may optionally include additional, unlisted elements or method steps.

[0058] As used herein, “and / or” means “any one or two” of such combined elements, that is, elements that exist together in some cases and separately in others. Multiple elements listed using “and / or” should be interpreted in the same way, that is, “one or more” of such combined elements. In addition to the elements specifically indicated by the “and / or” clause, other elements may optionally exist, whether related to or unrelated to those specifically indicated. Thus, as a non-limiting example, a reference to “A and / or B” used in conjunction with open-ended language such as “comprising” may, in one embodiment, refer only to A (optionally including elements other than B); in another embodiment, refer only to B (optionally including elements other than A); in yet another embodiment, refer to A and B (optionally including other elements); and so on.

[0059] As used in this article, "additive manufacturing" is also known as "additive fabrication," "layer-by-layer manufacturing," "solid freeform fabrication," "forming metal deposition," and "layer-by-layer manufacturing," and refers to an additive process that manufactures an object layer by layer. This process can utilize 3D model data, a source of metal raw materials (such as wire or powder), a heat source (such as a plasma arc, laser, or electron beam) to melt the metal source, or a combination thereof.

[0060] As used in this article, "additive manufacturing system" refers to a system used for additive manufacturing.

[0061] As used in this article, “directional energy deposition” or “DED” refers to an additive manufacturing process in which a heat source is used to fuse the material (particularly metals) by melting it as it is deposited.

[0062] As may be used interchangeably herein, the terms “plasma transfer arc torch” or “PTA torch” refer to any device capable of heating and exciting an inert gas stream into plasma by an electric arc discharge, and then transferring the plasma gas stream, including the arc, through an orifice (e.g., a constricting nozzle) to form a highly collimated column of ionized plasma gas that exits the nozzle orifice at high speed and transfers the intense heat of the arc to a target area, such as a wire or substrate.

[0063] As used herein, the term "metallic material" refers to any known or conceivable metal or metal alloy that can be used in a directional energy deposition process to form three-dimensional objects. Examples of suitable materials include, but are not limited to, titanium and titanium alloys, such as the Ti-6Al-4V alloy.

[0064] As used herein, "heat source" refers to a portion of a device from which thermal energy can be transferred to a metallic material (e.g., wire or metal powder), or to a substrate or base material, or any combination thereof. Exemplary heat sources include plasma arcs, laser beams, and electron beams.

[0065] As used herein, “melting tool” refers to an apparatus that generates a heat source for preheating or melting a portion or both of the surface of a metal material or workpiece in a DED additive manufacturing process. Examples include PTA welding torches that generate arc plasma as a heat source, laser apparatuses that generate laser beams as heat sources, and electron beam apparatuses that generate electron beams as heat sources.

[0066] As used herein, the term "base material" refers to the target material on which molten metal will be deposited to form the workpiece. This will be the substrate when the first layer of metal material is deposited. Once one or more layers of metal material have been deposited on the substrate, the base material will be the upper layer of deposited metal material on which a new layer of metal material will be deposited.

[0067] As used herein, the term "workpiece" refers to a metal body or object manufactured using directional energy deposition.

[0068] As used interchangeably herein, the terms "computer-aided design model" or "CAD model" refer to any known or conceivable virtual three-dimensional representation of an object to be formed, which can be used in a DED system to adjust the position and movement of a substrate and to operate the DED heat source and a source of metallic material (e.g., a metal powder supply or wire feeder) such that a physical object is constructed by continuously depositing metallic material to a pattern that results in the physical object being constructed according to the virtual three-dimensional model of the object and then fusing it onto the substrate. This can be obtained, for example, by first dividing the virtual three-dimensional model into a set of virtual parallel layers and then dividing each parallel layer into a set of virtual quasi-one-dimensional blocks to form a virtual vectorized layered model of the three-dimensional model. The physical object can then be formed by a coupling controller to deposit and fuse a series of quasi-one-dimensional blocks of metallic material fed onto the substrate according to the pattern of the first layer of the virtual vectorized layered model of the object.

[0069] Then, the sequence of the second layer of the object is repeated by depositing and fusing a series of quasi-one-dimensional blocks of weldable material onto the previous deposited layer in a pattern according to the second layer of the object's virtual vectorized layered model. For each successive layer of the object's virtual vectorized layered model, the deposition and fusion process is repeated layer by layer until the entire object is formed. However, the invention does not depend on any particular CAD model and / or computer software used for the controller to operate the device according to the invention, nor does it depend on any particular type of controller. Any known or conceivable controller (CAD model, computer software, computer hardware, and actuators, etc.) capable of constructing three-dimensional metallic objects by directional energy deposition can be used.

[0070] As used herein, "cooling gas" is a gas directed at a solidified surface, for example, towards a melting trajectory, to directly influence and accelerate the cooling and solidification of the solidified metal. The temperature of the gas can be any temperature at which it cools the surface it interacts with. This temperature can be less than 100°C, or less than 50°C, or less than 30°C, or less than 25°C, or less than 10°C, or less than 5°C, or less than 0°C, or in the range of approximately -10°C to approximately 100°C, or approximately -5°C to approximately 90°C, or approximately 0°C to approximately 80°C. The temperature can also be approximately 25°C or lower.

[0071] As used in this article, "residual stress" is the stress that remains in the structure even after all external loads have been removed due to the non-uniformity of residual strain. Residual stress is typically self-balancing.

[0072] As used herein, a "fixture" refers to a means for holding or securing a workpiece, mold, and clamp in place during deposition. For example, a fixture may include a tray, base, or platform to which the substrate or other portion of the workpiece may be secured during the DED process.

[0073] As used in this article, a "preform" is a workpiece produced through additive manufacturing processes. A preform can be an intermediate part between a finished product and a semi-finished product. A preform may have a net shape close to that of the final product and may require some (if minimal) further processing. For example, a preform may require final finishing to a high-tolerance construction.

[0074] As used in this article, the "buy-to-fly ratio" or "BTF ratio" refers to the weight ratio of the raw materials used to make the part to the weight of the finished product. This ratio can depend on how closely the shape of the initial deposited DED preform resembles the shape of the final part. The more material that needs to be removed from the DED preform to make the final part, the higher the BTF ratio.

[0075] As used in this article, the “length” or “length direction” of a substrate refers to the direction along the largest of the three dimensions of the substrate.

[0076] As used in this article, the “width” or “width direction” of a substrate refers to the direction along the second largest of the three dimensions of the substrate, typically a measurement from one short side to the other.

[0077] As used in this article, the “thickness” or “thickness direction” of a substrate refers to the direction along the smallest of the three dimensions of the substrate.

[0078] As used in this article, "high-strength steel" refers to steel with a tensile strength of 300 MPa or greater.

[0079] As used in this article, "high-strength low-alloy steel" refers to steel with a tensile strength of 370 MPa or greater.

[0080] As used in this article, "ultra-high strength steel" refers to steel with a tensile strength of 780 MPa or greater.

[0081] As used in this article, "warm forming temperature" is a temperature below the recrystallization temperature of a material that maximizes its ductility while preventing recrystallization, grain growth, or metallurgical fracture. Warm forming temperatures can range from approximately 200°C to approximately 850°C, depending on the material.

[0082] As used in this article, "thermoforming temperature" is a temperature above the recrystallization temperature of the material. The thermoforming temperature can range from approximately 600°C to approximately 2000°C, depending on the material.

[0083] As used herein, "back side of substrate" refers to the side of the substrate that faces away from the deposition apparatus during DED fabrication. For example, during deposition, the back side of the substrate may be directed toward a fixture. The back side of the substrate is the side opposite to the side where deposition occurs.

[0084] As used herein, "front side of substrate" refers to the side of the substrate facing the deposition apparatus. For example, the front side of substrate can be the side on which molten material is deposited during DED. The front side of substrate can be the side on which a workpiece is formed by DED. The front side of substrate is the side opposite to the rear side of substrate.

[0085] As used in this article, a "cavity" refers to any unfilled space or void within a material that does not penetrate the material to form a hole. A cavity can be a hollow space or a perforated space, or it can be a space formed by adding additional material.

[0086] As used in this article, the "nominal die deflection" or "h" of a bending clamping die. mold "(Bow-shaped)" is the difference between the maximum height of the bow-shaped surface measured at the center of the bow-shaped surface and the top surface of the edge of the curved clamping mold.

[0087] It should also be understood that, unless explicitly stated to the contrary, in any method claimed herein that includes more than one step or action, the order of the steps or actions of the method is not necessarily limited to the order in which the steps or actions of the method are described.

[0088] B. Bending clamping mold

[0089] Conventional die-casting (DED) of metals used in the production of preforms can introduce residual stresses into the preforms. These residual stresses during metal DED are typically caused by the fact that different areas of the manufactured part undergo varying cycles of thermal expansion and contraction. The resulting thermal stresses can lead to a non-uniform distribution of irreversible material deformation, some of which can remain after the material cools, creating an internal and completely self-balancing stress field within the workpiece. If this stress is not relieved, it can lead to numerous manufacturing defects. Figures 1A to 1H As shown, conventional DED additive manufacturing without stress relief is used ( Figure 1A The produced workpieces may exhibit mismatch ( Figure 1B and Figure 1C ),rupture( Figure 1D , Figure 1E and Figure 1F ) and tearing ( Figure 1G and Figure 1H An apparatus is provided comprising a bending clamping die as a lower support structure for pre-bending a substrate to manufacture single-sided metal parts with no residual stress and no distortion, or metal parts with reduced residual stress or reduced distortion, by means of de-emulation (DED). The apparatus can be used with a conventional DED heat source for melting metal powder or filament raw materials, or combinations thereof. The bending clamping die includes a first side having a peripheral edge having a flat or planar surface, creating a cavity or recess with one or more void regions, and one or more reinforcing members. The planar periphery and the reinforcing members share a common plane. Only the peripheral edge and the reinforcing members contact a clamp or clamping platform. The bending clamping die also includes a second side opposite the first side, the second side having a bent surface, such as… Figure 2A and Figure 8B As shown.

[0090] In use, the first side of the clamping die may point towards the welding fixture. The bent side of the clamping die may be guided away from the fixture and toward and positioned against the pre-bent substrate. The flat surface of the peripheral edge of the bent clamping die and the reinforcing members may rest flat on the fixture surface. One or more clamps may be used to secure the pre-bent substrate to the fixture. This may cause the pre-bent substrate to be pressed against the fixture, so that the force necessary to secure the pre-bent substrate to the fixture will be between the clamps and the fixture, wherein the bent clamping die acts as a support between the substrate and the fixture. In an embodiment, the pre-bent substrate is pressed axially downward.

[0091] Due to the contact between the bending die and the pre-bent substrate, some compressive stress can be felt on the bending die. The bending clamping die can be made of a rigid material that resists twisting and deformation to help maintain its shape. Additionally, the bending clamping die can be made of a material that is resistant to thermal shock, corrosion, and is non-magnetic.

[0092] A bending clamping die can be used as a support structure for a pre-bent DED substrate, located between the pre-bent DED substrate and a clamp. An exemplary device may include a clamp as the lowermost surface, on which the bending clamping die is positioned. The bending clamping die is positioned such that a first surface of the bending clamping die faces the clamp. A planar surface of the peripheral edge of the first side of the bending clamping die and reinforcing members may rest flat on the clamp surface. The rear side (first side) of the pre-bent substrate (on which a melt trail may exist) is positioned such that it faces the side of the bending clamping die (away from the clamp (second side)), in which the rear side of the pre-bent substrate faces downward toward the bent surface of the bending clamping die and the clamp. One or more clamps may hold the pre-bent substrate to the clamp, wherein the bending clamping die is between the pre-bent substrate and the clamp, and the force applied to the pre-bent substrate by the clamps may bring the pre-bent substrate into full contact with the bent second side of the bending clamping die, straightening the pre-bent substrate and forcing it to conform to the curvature of the second side of the bending clamping die. The one or more clamps surrounding at least a portion of the periphery of the DED substrate can compress the pre-bent substrate uniformly downward toward the clamp and can secure the pre-bent substrate to the clamp.

[0093] If the critical buckling stress of the substrate is exceeded, a bending die can help mitigate or eliminate deformation, such as weld-induced buckling distortion, which results from elastic instability caused by compressive residual stress. Due to thermal insulation on the second surface of the bending die, or on the cavity in the first surface of the bending die, or a combination thereof, the development of localized temperature gradients that can cause large localized contamination and resulting deformed patterns can be minimized. The bending die maintains a consistent connection with the pre-bent substrate to optimize thermal and mechanical uniformity on the pre-bent substrate.

[0094] Choose the size of the substrate to accommodate one or more workpieces to be constructed on it. Generally, the only limitation regarding the size of the bending clamping die relative to the substrate is that the substrate must be able to be clamped to the fixture, where the bending clamping die is positioned between the substrate and the fixture. The bending clamping die can be designed to be the same size as the substrate. Alternatively, the bending clamping die can be designed to be 0.5% to 10% larger than the substrate, provided the substrate can be clamped to the fixture.

[0095] The bending clamping die can be designed to be 0.05% to 2.5% smaller than the substrate, as long as the substrate does not contact the fixture when clamped onto it, with the bending clamping die positioned between the substrate and the fixture. Generally, it would be undesirable if the bending clamping die were significantly smaller than the substrate, as this would affect manufacturing consistency. The thermal conditions outside the die / substrate connection area will be different; in particular, areas that are not in contact with each other may experience different heat transfer conditions and therefore residual stress distributions.

[0096] The bending clamping die is thicker at the center than at the edges, resulting in a bending surface with maximum height near the center. In the embodiments provided herein, the height of the bending clamping die, measured at or near the center, can range from approximately 3 mm to approximately 60 mm, or from approximately 12 mm to approximately 50 mm, or from approximately 15 mm to approximately 45 mm. The height of the bending clamping die, measured at or near the outer edge, can range from approximately 0.5 mm to approximately 55 mm, or from approximately 3 mm to approximately 45 mm, or from approximately 10 mm to approximately 40 mm. When viewed from the side, the thickness profile of the bending clamping die has maximum height at the center, and this height gradually decreases towards the outer edge to form the bending surface. The height difference across the cross-section of the bending clamping die results in a downwardly concave curve in the top surface of the bending clamping die. In a cross-section viewed from the side, the shape of the bending clamping device can resemble the upper half of an ellipse, where the minor axis is much smaller than its major axis. An ellipse can have an eccentricity close to but less than 1 (an eccentricity of 1 would result in a flat surface).

[0097] The thickness of the bending clamping die can be designed to mimic or provide the same or similar thermal insulation properties as those achieved by ceramic insulating sheets conventionally used in DED processes. For example, one or more alumina (Al₂O₃) insulating sheets or plates are used in conventional DED processes to thermally separate the substrate from the clamping platform (e.g., a fixture). The conventional use of insulating sheets is to reduce the potential risk of thermal damage to the fixture while contributing to a more uniform temperature distribution during the DED process. While the thickness of the sheet or plate can vary, commonly used sheets can be approximately 3 mm to 3.5 mm thick. Multiple ceramic insulating sheets can be used in conventional DED processes. For example, in some conventional methods, approximately four ceramic insulating sheets or plates are used to provide an insulation layer of approximately 12 mm. More or fewer ceramic insulating sheets can be used conventionally. These alumina insulating plates can be cut to a certain size, but doing so releases alumina particles that can cause respiratory or eye irritation. Alumina insulating sheets also tend to absorb moisture and initially release water vapor during the heating temperatures of the DED process, which can cause undesirable fluctuations in the deposition environment during processing. The ceramic insulating sheet, which is conventionally used between the substrate and the fixture, must also be discarded after use due to its brittleness and fragility, thus representing a consumable that increases the manufacturing cost of DED.

[0098] Bending clamping dies can be used in combination with conventional ceramic insulating plates. Bending clamping dies can replace traditional ceramic insulating plates and provide similar thermal insulation while maintaining the same height, minimizing changes to the setup of the melting tool providing the heat source or the CAD-CAM path planning of the parts manufactured by DED. As mentioned above, there are no physical limitations on the thickness of the bending clamping die, except for constraints dependent on the machine's operation. For example, the height stroke of the DED system can dictate the thickness of the bending clamping die used. The thickness of the bending clamping die can be selected to maximize heat flow reduction at the die / clamp interface while allowing sufficient clearance for workpiece manufacturing based on the system's height stroke.

[0099] Bending clamping dies can be made of any metal with sufficient strength and temperature resistance to be used under typical DED processing conditions. Bending clamping dies can be made of corrosion-resistant metals. Bending clamping dies can be made of heat-resistant metals. Bending clamping dies can be made of non-magnetic metals. Bending clamping dies can be made of metals with a melting point of 1350°C or higher. In some constructions, bending clamping dies contain austenitic stainless steel. Austenitic stainless steel may contain carbon, chromium, copper, manganese, molybdenum, nickel, nitrogen, phosphorus, silicon, or combinations thereof. Austenitic stainless steel may contain at least 18% chromium. Bending clamping dies can be made of 300 series stainless steel. Bending clamping dies can be made of stainless steel series 304, 309, 310, 316, 318, 321, or 330. Bending clamping dies can be made of AISI 330 grade stainless steel. The bending clamping die can be made of a non-magnetic metal to avoid unbalanced magnetic field conditions around the welding arc in an arc-based DED system, which can cause many processing problems, such as arc blow.

[0100] To minimize or prevent heat transfer from the substrate to the top surface of the bending die during the DED process, the bending die may include a ceramic coating. For example, a ceramic coating may be applied to the surface of the bending die facing the DED substrate (containing a second bent surface with knurling or corrugation), such as... Figure 2B As shown. The ceramic coating can be applied directly to the curved surface, or the ceramic coating can be applied to an adhesive coating applied directly to the second curved surface. The ceramic coating can be applied directly to the opposing first flat surface of the mold, or the ceramic coating can be applied to an adhesive coating applied directly to the first flat surface. The ceramic coating can provide thermal insulation to minimize or prevent thermal contact between the bending clamping mold and the pre-bent substrate.

[0101] Any process can be used to apply the ceramic coating, including atmospheric plasma spraying, magnetron sputtering, chemical or electrochemical deposition (e.g., electrophoretic deposition), or physical vapor deposition (e.g., electron beam physical vapor deposition). Any high-temperature ceramic coating known in the art can be used (e.g., see U.S. Patents 4,321,310 (Ulion et al., 1982), 5,789,330 (Kondo et al., 1998), 5,304,519 (Jackson et al., 1994); 6,387,539 (Subramanian, 2002); and 6,998,064 (Gadow et al., 2006). Exemplary types of ceramic coatings include zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, alkaline earth metal silicates, ZrV₂O₇, Mg₃(VO₄)₂, and combinations thereof. Bending clamping dies can be coated with zirconium dioxide stabilized by the addition of yttrium oxide, such as plasma-sprayed ZrO₂·8Y₂O₃, for example, commercially available as Metco. TM Those obtained from 22xx and 23xx include Metco 222A, 231A, 233B, 233C, and 234A (available from Oerlikon Metco in Frankfurt, Germany). The coating may comprise multiple layers of different types of ceramic, or multiple layers of a single type of ceramic.

[0102] The ceramic coating used on the bending clamping die can be selected to be less hygroscopic than conventional alumina insulation. Alternatively, the ceramic coating used on the bending clamping die can be selected to be non-hygroscopic compared to conventional alumina insulation. Replacing conventional ceramic insulation sheets with bending clamping dies results in a significantly more stable processing chamber atmosphere because less water vapor, or no water vapor at all, is released from the ceramic coating of the bending clamping die into the processing chamber during the DED process compared to the amount released from conventional alumina ceramic plates.

[0103] Bending clamping dies may include an adhesive coating. The adhesive coating is a material coating that increases adhesion between a substrate and a ceramic coating. The adhesive coating can provide corrosion resistance to the substrate to which it is applied. The adhesive coating can be used alone or in combination with a ceramic coating. The adhesive coating may include chromium and aluminum. The adhesive coating may include MCrAlY, where M is a metal selected from the group consisting of Co, Ni, Fe, Cr, Co, and Ni / Co combinations. In some applications, the adhesive coating includes MCrAlY, where M is Ni, Co, or a combination thereof. Exemplary adhesive coating materials include Amdry. TM Powder products, such as Amdry TM 962, 9621, 9624, 9625, 963 and 964 (available from Oerlikon Microelectronics in Frankfurt, Germany). The adhesive coating can be present in thicknesses from approximately 1 to 250 μm. Figure 2C An exemplary embodiment is schematically illustrated. The ridge 120 is coated with an adhesive coating 155, which is subsequently coated with a ceramic coating 150.

[0104] The thickness of the ceramic coating applied to the bending clamping die can vary depending on the type of ceramic used and its ability to withstand mechanical and thermal loads. In some configurations, the overall thickness of the ceramic coating can be from about 0.1 mm to about 5 mm, or from about 0.25 mm to about 4 mm, or from about 0.3 mm to about 3 mm. Each deposited layer can be thinner than the total amount of ceramic coating to be applied, but in general, all applied ceramic layers can together form a ceramic coating of at least 0.1 mm, or at least 0.25 mm, or at least 0.5 mm, or at least 0.75 mm, or at least 1 mm, or at least 1.25 mm, or at least 1.5 mm, or at least 2.0 mm, or at least 2.5 mm, or at least 3.0 mm, or at least 3.5 mm, or at least 4.0 mm, or at least 4.5 mm. The ceramic coating can have a thickness of 0.1 mm, or 0.25 mm, or 0.5 mm, or 0.75 mm, or 1 mm, or 1.25 mm, or 1.5 mm, or 2.0 mm, or 2.5 mm, or 3.0 mm, or 3.5 mm, or 4.0 mm, or 4.5 mm, or 5 mm. The ceramic coating helps reduce heat transfer from the pre-bent substrate to the bending clamping die, thereby reducing heat loss from the pre-bent substrate during DED.

[0105] To further minimize or prevent thermal communication between the bending die and the pre-bent substrate, the bending surface of the bending die can be physically modified. A knurled surface can be cut into the bending surface of the bending die before applying a ceramic coating. A corrugated surface comprising a combination of ridges and grooves can be cut into the bending surface of the bending die before applying a ceramic coating. A corrugated surface comprising a combination of ridges and grooves can be cut into the bending surface of the bending die before applying a ceramic coating, wherein one or more ridges have a knurled surface. Figure 2A , Figure 2B , Figure 3A and Figure 3B An exemplary implementation is shown in the figure. Figure 2A The illustrated embodiment shows a bending clamping die 100, which includes a corrugated top surface 110 comprising a combination of ridges 120 and grooves 130, and a bottom surface having a flat or planar edge 140. The bending clamping die may include edges 115 on each side, such as… Figure 2B As shown. The edge 115 on each side of the mold helps to support and / or limit the downward movement of the short edge of the plate (substrate) during clamping.

[0106] In the embodiments provided herein, the bent surface of the bending clamping die includes knurling. The knurled surface on the bent surface of the bending clamping die can produce a straight line pattern, a diagonal pattern, a diamond pattern, or a combination thereof on the surface. Diamond knurling can be performed to produce convex or concave knurled patterns. In a convex diamond pattern, raised dots are produced. In a concave diamond pattern, diamond indentations are produced. Knurling can produce multiple pillars, each pillar having a straight edge substantially perpendicular to the curvature arc of the bending clamping die. The pillars can have a flat top surface. The pillars can have a bent top surface. The pillars can have a cross-section of a square, rectangle, circle, ellipse, diamond, trapezoid, triangle, pentagon, hexagon, heptagon, nonagon, decagon, truncated pyramid shape, truncated pyramid shape, or any combination thereof. The pillars can be spatially separated from each other. The gap between the pillars can be substantially constant.

[0107] In the embodiments provided herein, the bending surface of the bending clamping die may include corrugations or a corrugated shape. The bending surface of the die may be corrugated to include alternating ridges and grooves. Corrugations may extend from one long edge of the bending clamping die to another long edge. Corrugations may extend from one short edge of the bending clamping die to another short edge (e.g., see...). Figure 3A and Figure 3B The corrugations create multiple columns perpendicular to the curvature arc of the bending clamping die. The peripheral edge of the die at the bending surface can be contoured with a metallic material and is not coated with a ceramic or adhesive coating.

[0108] A ridge can be a column with a flat top surface. A ridge can be a column with a curved top surface. A groove can have a flat bottom surface, or a curved or U-shaped bottom surface. Grooves can include rounded corners to prevent stress concentration and crack propagation. Each ridge can have a tapered shape that increases in cross-section along its longitudinal axis. In cross-section, a ridge can have a trapezoidal shape. In cross-section, a ridge can have an isosceles trapezoidal shape, wherein the longer base of the trapezoid forms the bottom of the ridge, and the shorter base of the trapezoid forms the top of the ridge. In cross-section, a ridge can have a convex isosceles trapezoidal shape. In cross-section, a ridge can have the shape of a truncated pyramid. Figure 2A , Figure 2B , Figure 2C and Figure 3B An exemplary spine is shown in the figure.

[0109] Ridges with a truncated pyramidal shape (especially a truncated pyramidal shape) in cross-section can transfer stress from the top of the ridge to the base, while avoiding stress deformation of the ridge due to pressure applied to the bent surface of the bending clamping die when the pre-bent substrate is attached to the fixture. Ridges with a truncated pyramidal shape in cross-section can withstand the loads, forces, and moments that can be applied during the DED process. Forces and moments acting on the platform (upper plane) of the ridge can be transferred to the base of the ridge and ultimately to the rear side of the bending clamping die. When the ridge's cross-section is truncated pyramidal, it can transfer the applied load to a larger surface area at the base of the ridge. When the bending clamping die is brought into contact with the pre-bent substrate, the knurled surfaces or grooves between the ridges create a gap between the bent surface of the bending clamping die and the pre-bent substrate. This gap can be filled with the atmosphere of the DED chamber or an inert gas (e.g., argon), which can serve as a thermal insulator. Argon is a very effective thermal insulator. The solid / gas / solid interface has relatively low conductivity, so these specific interfaces between the pre-bent substrate / argon / bending clamping die will effectively serve as thermal barriers. Therefore, this gap also helps minimize the average heat transfer coefficient between the pre-bent substrate and the bending clamping die. The combination of knurled surfaces or ridges and grooves on the bending surface of the bending clamping die further minimizes the actual contact area between the pre-bent substrate and the bending clamping die, thereby further reducing heat transfer and thus retaining the maximum amount of heat in the pre-bent substrate and preventing heat transfer to the clamping or welding station. Therefore, bending clamping die designs that include knurled or corrugated surfaces on the bending surface and a ceramic coating on the bending surface effectively reduce conductive heat transfer from the pre-bent substrate to the bending clamping die. Since the thermal gradient across the thickness of the pre-bent substrate can be significantly smaller during the deposition of the first layer, the residual stress caused by welding generated during the DED of the metal preform will be reduced. Moreover, because titanium and titanium alloys (e.g., Ti-6Al-4V) have high yield stress and relatively low elastic modulus, these metals exhibit high resilience at room temperature. Reducing conductive heat transfer from the pre-bent substrate to the bending clamping die can promote heat accumulation in the substrate during the DED process, thereby minimizing springback.

[0110] The knurling pattern or corrugations on the curved surface of the bending clamping mold may have a ceramic coating on its surface, as described above. Figure 2BAn exemplary embodiment of a bending clamping die 100 with a ceramic coating 150 is shown. Since ceramic is typically applied to the surface of the bending clamping die to form a ceramic coating, the ceramic coating can also be present in knurled or corrugated grooves. The thickness of the ceramic coating is limited only by the amount applied to the die, the ceramic thickness's ability to support the pre-bent substrate, and the downward clamping force, without damaging the ceramic coating when the substrate is clamped to the fixture. Due to limitations in coating techniques, thicker ceramic layers are more difficult to achieve while maintaining the ceramic layer's ability to support the pre-bent substrate without damaging the ceramic coating when the support is clamped to the fixture. The exact support strength and thermal conductivity of the ceramic can be determined by the ceramic's composition. For example, a 2mm zirconium dioxide-based ceramic coating stabilized by the addition of yttrium oxide can provide good thermal insulation and good mechanical support for the substrate without damaging the ceramic coating when the substrate is clamped to the fixture.

[0111] A bending clamping die can be used as a forming support structure. In an embodiment, the bending clamping die can be used as a support / forming support structure. When the pre-bent substrate is secured to the fixture, the bending clamping die can be positioned between the pre-bent substrate and the fixture. The pre-bent substrate can be clamped to the fixture such that the substrate is in full contact with the bent upper surface of the bending clamping die (e.g., approximately 95% to 100% contact). When the DED manufacturing process is complete, a self-balancing residual stress state is achieved, which allows for upward recovery (springback) of the substrate and the DED structure built on the substrate after the fixture holding the substrate to the fixture is released. After the substrate is released from the fixture, the substrate is straightened.

[0112] The nominal die deflection h of the bending clamping die mold (Arch) is the difference between the maximum height at the center of the curved surface of the bending clamping die and the upper surface of the edge of the bending clamping die, as shown in Figure 2. Figure 2B In the middle, the difference between the maximum height 180 of the bent surface and the edge 115 of the bending clamping die is h. mold The mold length is greater than L. r The new x-size L of the mold i The ratio between the original mold length L0 and the predicted maximum mold deflection h. Lr Approximately the nominal mold deflection h mold The ratio L to the mold length calculated according to the following formula r The products of the squares of the two are proportional:

[0113] L r =L i / L0

[0114] And therefore

[0115] h Lr ≈h mold ×Lr 2 .

[0116] Therefore, for a bending clamping die with xy dimensions of 635mm × 190mm (L × W), the predicted maximum die deflection h is... Lr It is approximately 3.8mm. Longer dies, such as a bending clamping die with xy dimensions of 1905mm × 635mm, will have a die length ratio of 3 (L...). r =1905 / 635=3) and 3.8×3 2 Maximum mold deflection h ≈34.2mm Lr The nominal die deflection can range from approximately 3 mm to approximately 35 mm. Therefore, the amount of die deflection can depend on the characteristics of the die. Bending clamping dies require longer lengths to accommodate longer substrates, and the deflection of bending clamping dies will need to be higher / greater.

[0117] Bending clamping dies can also be designed so that the lower side of the die includes a cavity or recess, while still maintaining the die's rigidity and resistance to deformation. Figure 4 An exemplary design is illustrated. A segment of non-magnetic metal on the bottom surface of the bending clamping die can be machined away to create two or more cavities or recesses. These cavities or recesses can be separated from each other by unmilled metal regions that can serve as reinforcing members. Unmilled metal regions may also exist around the periphery of the bottom surface of the die to form edges. This design reduces the amount of material required to manufacture the bending clamping die while still maintaining the physical stability of the die. By reducing the required volume of material used to form the die, the weight of the die can be reduced while maintaining the rigidity of the die structure. As an alternative to milling the metal to achieve the desired cavities and reinforcing members, a casting die can be used to manufacture the bending clamping die by casting to include these properties, thereby minimizing the amount of material that needs to be removed to achieve the desired final design. Furthermore, reinforcing members can be added, for example, by attaching separately prepared reinforcing members to the bottom surface of the bending clamping die. The reinforcing members can be attached via any suitable method. Exemplary methods include welding, screws, bolts, adhesives, or combinations thereof.

[0118] The cavity can have any shape. The cavity can be four triangular cavities separated by mold material to form an X-shaped reinforcing member that separates the cavities from each other. Figure 4An exemplary embodiment is shown. In the illustrated configuration, the substrate is machined to create triangular cavities 160, 162, 164, and 166, while leaving material to form an X-shaped reinforcing member 170 and a straight peripheral edge 140. The outer surface of the straight peripheral edge 140 and the outer surface of the X-shaped reinforcing member 170 are in the same plane and can lie flat on the fixture surface when fixed to a fixture. The cavities can be four square or rectangular cavities separated by a mold material to form H-shaped reinforcing members that separate the cavities from each other. The cavities can be any shape selected from squares, rectangles, circles, ovals, ellipses, trapezoids, parallelograms, pentagons, hexagons, heptagons, starbursts, crosses, polygons, intersecting geometries, polygons, geometric shapes, irregular shapes, regular shapes, symmetrical shapes, asymmetrical shapes, and combinations thereof.

[0119] In addition to cost savings achieved by reducing the amount of non-magnetic metal required for fabrication, the cavity reinforcement and peripheral edge design offers several functional advantages. One advantage is that only the unmilled portion of the bottom surface of the die will come into contact with the high-strength steel fixture. This reduces conductive heat transfer from the bending die to the fixture while maintaining the rigidity of the bending die. This reduction in heat transfer also helps retain heat in the pre-bent substrate, thereby minimizing fixture loss.

[0120] Additionally, the cavity in the bottom surface of the bending clamping die can hold an atmosphere or argon. Due to the presence of the cavity and surrounding edges, argon effectively serves as an insulator for most of the underside of the die. Argon is a very effective insulator. Any heat flow from the bending clamping die to the underlying steel fixture will be conducted only at the solid / solid interface due to thermal gradients. Because the thermal conductivity of the solid / gas / solid interface is significantly lower, the cavity in the lower surface of the bending clamping die effectively serves as a thermal barrier (e.g., an air or inert gas gap) between the bending clamping die and the fixture. Air or inert gas gaps can be utilized between the substrate and the clamping die, and / or at the interface between the clamping die and the fixture, to help reduce heat transfer from the substrate to the fixture. Therefore, the bending clamping die helps retain more heat in the pre-bent substrate, thereby further reducing uneven temperature distribution and thermal stress in the pre-bent substrate.

[0121] Bending clamping dies exhibit high durability. After repeated use, bending clamping dies may experience some thermal stress, which can accumulate cumulatively and cause a small degree of arcing distortion in the die (e.g., a lift of 0.05 mm to approximately 0.5 mm at the edges after repeated use). The degree of arcing distortion observed in the bending clamping die after repeated use is not expected to significantly alter the distortion mitigation effect produced on DED preforms. Different object designs may require the use of bending clamping dies of different sizes to accommodate substrates of different sizes. Similar bending clamping dies can be used to produce objects with similar geometries and / or substrate sizes. For example, objects with similar geometries and / or substrate sizes can be grouped into multiple families, and the same bending clamping die design can be used within the same object family.

[0122] The exemplary bending clamping mold provided herein can be freestanding. The bending clamping mold can be detached from and spaced apart from the fixture. In an exemplary embodiment, the bending clamping mold can be placed flat on the fixture. The exemplary clamping mold may include edges having a flat or planar surface around its perimeter. The curvature of the mold can be empirically determined based on data collected from initial experiments performed using ceramic plates. The ceramic plates are cut to different sizes and then used to generate different current curvatures, and their ability to minimize deformation in preforms prepared on the bending mold is tested. Modeling is then used to confirm that the curvature used experimentally provides the target end result, i.e., a preform approaching distortion-free. In a cross-section when viewed from the side, the shape of the bending clamping device can resemble the upper half of an ellipse, where the minor axis is much smaller than its major axis. This ellipse can have an eccentricity close to, but less than, 1 (an eccentricity of 1 would result in a flat surface).

[0123] The bending clamping die presented in this paper allows for simpler, lighter, cheaper, and more versatile redesign of clamps. Current clamps are over-designed to accommodate the anticipated reaction forces and stresses encountered when the substrate is directly clamped to the clamp and during DED (Displacement Erection). The bending clamping die reduces these anticipated forces and stresses. The bending clamping die presented in this paper also allows for modifications to the clamping device compared to conventional clamping devices. In some applications, the entire periphery of the substrate can be clamped to the clamp when using the bending clamping die.

[0124] C. Directed Energy Deposition Method

[0125] This paper provides a method for directional energy deposition (DED) that mitigates or reduces distortion in objects manufactured using DED, particularly in titanium and titanium alloy objects. The method includes: thermally pre-bending a substrate on which an object will be manufactured; attaching the pre-bent substrate to a bending clamping die provided herein; preheating the substrate prior to DED deposition; and producing the object by depositing metal layer by layer. The pre-bending of the substrate involves inducing a steep full-thickness thermal gradient within the substrate.

[0126] For the thermally induced pre-bending step, a heat source can be used to apply thermal energy at a high energy density to a surface on a first or rear side of the substrate. The thermal energy can be applied to a defined portion of the rear side of the substrate to create a large thermal gradient within the substrate. This large thermal gradient can introduce a high residual stress field into the substrate. The thermal energy can be applied, followed by a temperature reduction of the surface to which the thermal energy was applied. In an embodiment, a gas jet device can be used to apply a cooling gas. The application of the cooling gas can increase the cooling rate, thereby further increasing the stress applied to the substrate. For example, the heat source may include the arc of a plasma welding torch, such as a PTA welding torch, and the gas jet device may be attached relative to the plasma welding torch to a support, such as... Figure 5 As shown. In Figure 5 In this configuration, the gas jet device 200 is attached to the support member 230, and the nozzle 210 of the gas jet device 200 can apply cooling gas to the area heated by the PTA welding torch 250.

[0127] Conversely, in the preheating step, heat energy is applied uniformly to the surface of the substrate to minimize temperature gradients along the x, y, and z directions. Heat energy is applied as uniformly as possible to the front side of the substrate as the heating device allows. Any heating device or method that provides uniform heating can be used for preheating. For example, direct heating utilizing a heater positioned to apply heat to the surface of the substrate can be used. The heating device can be or includes an infrared heater, an induction heater, a resistance heater, or a combination thereof. Exemplary heaters include a conductor heat source within a conduit, a heater bar, a resistance heating bar, an infrared heater, a positive thermal coefficient ceramic heater, a thick-film ceramic heater, a resistance wire or resistance strip heating device, an infrared heater, and an induction heater. Preheating can also be achieved using one or more melting tools to apply heat energy to the surface of the substrate. Melting tools can be used alone or in combination with infrared heaters, induction heaters, resistance heaters, or combinations thereof. Melting tools can include arc plasma, a laser beam, or an electron beam as a heat source, and multiple melting tools containing the same or different heat sources can be used. By using lower energy densities and applying more heat energy over a larger area, the heating zone can be maximized. Multiple heating sources can be used one after another, in series or in parallel, to generate multiple thermal "lines" applied to the front surface of the substrate, thus heating the substrate more uniformly. This allows for the use of low energy density heating to more evenly raise the substrate temperature, resulting in little or no thermal gradient, especially along the entire thickness. Applying heat energy using one or more melting tools during preheating dry runs (applying heat without adding molten metal) results in the effective removal of any residual contaminants from the substrate surface, such as any contaminants left by any ultrasonic / manual wiping cleaning process. Preheating is performed until the target temperature of the substrate is reached.

[0128] In some applications, the target temperature achieved through the preheating process is the DED process temperature, such as the DED deposition temperature, or approximately ±25°C of the DED process temperature. In some applications, the target temperature is within ±25°C of the substrate's plastic deformation temperature. In some applications, preheating is performed until the substrate reaches a temperature of approximately 400–900°C. In some applications, preheating is performed until the substrate reaches a temperature of approximately 500–850°C. Other authors have reported that warm forming can also be performed between 200–300°C to reduce flow stress and also help minimize titanium springback. In some applications, preheating is performed until the substrate reaches a temperature of approximately 595–815°C.

[0129] When a pre-bent substrate is clamped into a fixture, the bending clamping die can be used as a support for the pre-bent substrate. Among other advantages, the bending clamping die provides a more consistent and reproducible distribution of residual stress at the ends and helps minimize workpiece distortion during and after manufacturing.

[0130] DED can be performed after the substrate has been preheated (and kept heated) to mitigate the generation of thermal gradients during the DED process, particularly along the full thickness (z-direction). While it is optimal to avoid introducing stress into the fabricated object, the DED process is an efficient welding process and will typically result in the unavoidable accumulation of residual stresses and deformations caused by welding during fabrication. Reducing these residual stresses and deformations leads to improved dimensional accuracy and superior mechanical properties in the object. The steps of this method are described in further detail below.

[0131] 1. Pre-bent substrate

[0132] In the method provided herein, the substrate can be pre-bent prior to deposition. Substrate pre-bending can be a separate step in the DED process. In the method provided herein, thermal energy can be applied to a first side of the substrate to plastically deform it, thus permanently and uniformly pre-bending the substrate. In embodiments, when thermal energy is applied to the surface of the first side of the substrate, one or more self-generated melting tracks or weld lines can be formed. This is significantly different from physically constraining and mechanically pre-bending the substrate using a clamp through mechanical stress. While mechanical pre-bending can be used to bend the substrate, the mechanical stress typically does not involve localized melting of a planned segment of the substrate surface and is insufficient to introduce the desired uniform plastic deformation into the substrate. The stress redistribution pattern introduced by mechanical force differs from the stress redistribution pattern introduced by applying localized heating after the substrate is released from the clamp. For example, when a substrate pre-bent under mechanical force is released, the substrate springs back to a much higher degree than in the case achieved by thermal pre-bending.

[0133] In one embodiment, the substrate may have a first side and an opposing second side. The first side may be the side facing the fixture during DED manufacturing, and the second side may be the side on which the workpiece is formed by the DED. For pre-bending, the substrate may be clamped in the fixture with the first side facing upward and the rear side facing downward toward the fixture.

[0134] Pre-bending of the substrate can be performed while the substrate is in a flat position. Pre-bending of the substrate can be performed while the substrate is securely attached to the fixture using multiple clamps. Pre-bending of the substrate can be performed while the substrate is thermally insulated from the fixture. Thermal insulation between the substrate and the fixture can be achieved by including one or more alumina insulating sheets of the same size as the substrate. In this embodiment, four alumina insulating sheets can be used. Other materials capable of providing thermal insulation between the substrate and the fixture can be used. A device with thermophysical properties similar to those of a bending clamping die can be used, such as a corrugated surface with a series of ridges and grooves having a ceramic coating that provides thermal insulation, but in a flat configuration rather than a bent configuration. Using such a device eliminates the need for using alumina insulating sheets or other insulating material sheets.

[0135] A jig can be used to hold the substrate along all four edges of the substrate using a jig that surrounds the entire perimeter of the substrate. In some applications, the jig can be used to attach the substrate to the jig only along the two longest opposing edges of the substrate. This configuration allows heat sources (such as arc plasma, lasers, electron beam devices, or any combination thereof) to reach the furthest edges of the substrate along the length direction. This clamping device allows energy to be transferred from edge to edge and can generate a stress field all the way to the edge of the substrate, which can help counteract subsequent residual stresses introduced in this particular region during DED manufacturing.

[0136] It has been found that applying strong heat energy all the way to the edge or within approximately 5 mm of the edge minimizes or prevents substrate distortion. Distortion increases with the distance from the edge to the end where strong heat energy is applied. The thermal stress generated when a DED heat source is applied up to 10 mm from the edge is significantly different from the thermal stress achieved when the heat source is applied at the edge or only up to 20 mm from the edge. It has been found that substrate thickness makes little difference when considering the permissible distance from the edge without causing stress formation. Thicker substrates may require higher arc energy (or heat input) to be delivered during pre-bending, allowing for wider and deeper fusion profiles. This can be achieved, for example, by reducing the traverse speed, increasing the heat energy applied, or a combination of both. Taller DED preform shapes may also have less distortion compared to shorter shapes, meaning that the die radius of curvature can be increased for shorter shapes.

[0137] Clips are used to attach substrates to fixtures, and a constant clamping force can be applied to all clips. This is achieved by controlling the tightening torque of the bolts that connect the clips to the fixtures. During the pre-bending stage, a force ranging from 10 Nm to 20 Nm, such as 15 Nm, can be used to tighten the bolts connecting the clips to the fixtures. Higher torques can be used for thicker substrates.

[0138] A DED heat source generates heat to sufficiently melt planned segments on the substrate surface in a predetermined sequence or location, or both, thereby forming a self-generated melt line on the substrate surface. A gas jet device can be used to direct cooling gas toward the melt path for rapid cooling. Heating or a heat / cooling thermal cycle can induce the controlled formation and development of residual stress in the substrate. As a result, uniform thermally induced pre-bending can be achieved, or controlled to a predetermined level as needed.

[0139] The DED heat source can be configured to provide sufficient thermal energy to induce a melting trajectory on the DED substrate at a relatively fast rate. When in use, a gas jet device can deliver a large volume of cooling gas, such as 100 L / min to 200 L / min, to apply a rapid heating / cooling cycle to the substrate surface. For example, using a plasma-transferred arc system with a substrate thickness of 9.5 mm–10 mm, a current of 190 amperes, a voltage of 25.5 V, and a traverse velocity of 10 mm / s, a melting trajectory approximately 3 mm wide and at most 1 mm deep can be generated. This corresponds to an arc energy delivery of approximately 485 J / mm. For thicker substrates, the energy and traverse velocity can be adjusted. Figure 6 An exemplary embodiment is shown. In the illustrated embodiment, a substrate 300 having a first side 310 is shown having melt tracks 350 and 360 on the first side 310, a space 355 between the melt tracks 350 and 355, and a DED back wall of a preform 330 on a second side 320 of the substrate 300.

[0140] In addition to the cooling gas from the gas jet device, the rapidly applied high temperature promotes a rapid cooling rate, which can result in a very steep thermal gradient around the melting trajectory and toward the substrate (along the x, y, and z directions). This allows for a high stress state close to the material yield strength of the substrate material.

[0141] Any gas jetting device configurable to deliver cooling gas to the molten surface of a substrate for rapid cooling can be used. For Ti or Ti alloys, an inert gas can be used as the cooling gas. The inert gas can be argon, helium, krypton, xenon, or a combination thereof. The gas jetting device may include a conduit, pipe, or other conduit, or a combination thereof, that can deliver cooling gas from a gas supply device to the application area. The gas jetting device may include a first end and a second end, the first end being attached to the gas supply device, and the second end being positioned to direct the cooling gas exiting the second end to a desired location on the substrate, such that the cooling gas impinges on the substrate surface, particularly in the region of molten metal along the melting trajectory. Multiple gas jetting devices can be used to enhance or accelerate the cooling of the melting trajectory. The second end of the gas jetting device may include one or more nozzles adjustablely positioned to direct the cooling gas to the target location. The impact effect of the cooling gas on the substrate surface is greatest near the direct impact of the cooling gas, but the surrounding area of ​​the substrate can also be advantageously affected to reduce the temperature near the cooling gas. Pulsed gas flow can be used to deliver the cooling gas. Fully turbulent gas flow can be used to increase cooling efficiency. Cooling gas injection devices are known in the art (see, for example, U.S. Patents 4,090,697 (Perrine, 1978); 6,390,115 (Rohwer et al., 2002); and 7,381,364, Yamashita, 2008). An exemplary gas injection device is described in U.S. Patent Application No. 16 / 019,460, filed June 26, 2018.

[0142] The conduit, pipe, or duct of the gas injection device can be made of any material having a through-extension channel compatible with the conditions expected during DED deposition. The gas supply device can be any source of cooling gas, such as a compressor or a high-pressure gas container in fluid communication with the gas injection device. Methods for delivering pressurized gas to the gas conduit are known in the art.

[0143] Cooling gas can be supplied to provide a target flow rate to impinge on the substrate surface. The gas flow rate can be greater than 50 L / min, or greater than 100 L / min, or greater than 150 L / min, or greater than 200 L / min. The gas flow rate can range from 50 L / min to 500 L / min. The gas flow rate can range from 50 L / min to 250 L / min. The gas flow rate can range from 50 L / min to 100 L / min. The flow rate can be selected for rapid cooling, thereby creating high thermal and high stress gradient conditions in the substrate.

[0144] The cooling gas may include inert gases such as argon, helium, neon, xenon, krypton, and combinations thereof. The cooling gas may be applied at a constant flow, intermittently, or in a pulsed flow. The temperature of the applied cooling gas can be any temperature. The cooling gas temperature may be the ambient temperature of the additive manufacturing process. The cooling gas temperature may be applied at a gas temperature of approximately 100°C or lower. The cooling gas temperature may be approximately room temperature or lower, such as approximately 25°C or lower. The cooling gas temperature may be in the range of approximately -10°C to approximately 80°C.

[0145] For a preform or workpiece to be formed on the second surface of a substrate, the number of DED walls having a centerline parallel to the short edge of the substrate and the number of DED walls having a centerline parallel to the long edge of the substrate can be determined. If most of the DED walls of the preform or workpiece have a centerline parallel to the short edge of the substrate, a melt trajectory parallel to the short edge of the substrate can be produced. Typically, substrates with a large aspect ratio will require a melt trajectory to be produced along their longest axis (i.e., the axis from which the greatest distortion effect is expected). If most of the DED walls of the preform or workpiece have a centerline parallel to the long edge of the substrate, the melt trajectory can preferably be produced parallel to the long edge of the substrate to counteract the maximum distortion effect along the longest axis of the substrate.

[0146] Thermally induced pre-bending can be applied to the first or rear side of the substrate, such that the resulting melt trajectory and the typical distribution of longitudinal and transverse residual stresses caused by welding are positioned approximately 10 mm to approximately 20 mm away from the centerline of most of the DED wall of the preform or workpiece to be deposited on the second or front side of the substrate. A pre-bending forming technique applied to the first side of the substrate can be performed such that the resulting melt trajectory is positioned approximately 10 mm, or 11 mm, or 12 mm, or 13 mm, or 14 mm, or 15 mm, or 16 mm, or 17 mm, or 18 mm, or 19 mm, or 20 mm away from the centerline of the DED wall of the workpiece, which will be deposited parallel to the long edge of the substrate on the second or front side of the substrate. The melt trajectory can be positioned such that it can exist below a minimal area of ​​the DED wall of the workpiece. Figure 6 An exemplary implementation is shown in the figure.

[0147] Prior knowledge of the shape of the DED workpiece to be deposited on the second side of the substrate can be used to determine the pre-bending heating process applied to the first side of the substrate. This heating process can be designed to generate a minimum number of melt tracks below the area where the DED workpiece will be constructed. Compared to the original residual stress distribution of a DED without pre-bending melt tracks (i.e., a high tensile peak at the DED centerline and a lower equilibrium compressive stress further away), the final aggregated residual stress distribution resulting from the combination of the DED and the melt tracks has a lower tensile peak at the DED centerline and a lower equilibrium compressive stress further away from the DED centerline.

[0148] Figure 7A An exemplary implementation is illustrated, showing the application of thermal energy to create a melting trajectory on a substrate. This illustration schematically shows an exemplary heating path that can be used to move a DED energy source to create a melting trajectory on the top surface of the substrate on the rear or first side, so as to pre-bend the substrate toward the heat source. Black arrows indicate the direction / path of the DED energy source, including X... ES The circles indicate a sequence X, where X is 1 to 6 on the surface of the first side 310 of the substrate 300, where S indicates the start of the path and E indicates the end of the energy application path, thus obtaining a heating path. In the pattern shown, heating can occur at the top edge (1) in the x-direction. ES Starting at point ), the heat source can then move in the y-direction to a point less than half the length of the substrate, and can apply heat in the y-direction from the short edge to the short edge (2). ES For 3 ES 4 ES , 5 ES and 6 ES This process can be repeated. The first heating path 370 corresponds to 1. ES The second heating path 371 corresponds to 2. ES The third heating path 372 corresponds to 3. ES The fourth heating path 373 corresponds to 4. ES The fifth heating path 374 corresponds to 5. ES The sixth heating path 375 corresponds to 6. ES .

[0149] Pre-defined DED heating / cooling thermal cycles can induce controlled formation and development of residual stress in the substrate. Applying cooling gas using a gas jet device (not shown) can accelerate cooling. As a result, uniform thermally induced pre-bending of the substrate can be achieved / controlled to a predetermined level.

[0150] Figure 7B The diagram schematically illustrates heating paths 370 to 375 (denoted as 1). ES Up to 6 ESThe thermally induced pre-bending melt trajectory generated on the rear or first side of the substrate is positioned relative to the cover (gray dashed line) DED workpiece preform 600 to be manufactured on the rear or second side of the substrate. The melt trajectory can be generated by applying thermal energy in the heating path.

[0151] The heat source of the melting tool heats the back side of the substrate to form a melting trajectory at a predetermined location on the substrate, thereby applying thermal stress to the substrate. This thermal stress can cause the substrate to bend. Because the substrate can be firmly clamped to the fixture, the bending of the substrate is not noticeable when it is attached to the fixture. Once the clamp is removed, the substrate can bend upwards away from the fixture, i.e., in the direction of the heat source. The uniformly deformed pre-bent substrate can be defined by a clearly defined radius of the arc. After the clamp on the fixture has been removed, the uniform elastoplastic pre-bending effect obtained on the substrate due to the application of thermal energy... Figure 8A As shown in the diagram, the resulting substrate 300 bends upward away from the fixture 400 and exhibits nominal substrate deflection. Figure 8B In this process, the substrate is flipped up and down. For example... Figure 8B As shown, the pre-bent substrate has a uniform elastoplastic bend (bow shape) caused by the application of strong heat and cooling gas to induce a large temperature and stress gradient on the back side of the substrate. Figure 8B The nominal substrate deflection 410 is shown in the figure.

[0152] The thermally induced substrate pre-bending process can lead to a longitudinal residual stress distribution. A comparison of residual stress maps of several thermally pre-bent substrates as described herein demonstrates a characteristic distribution of residual stress, in which large tensile stresses are generated at the weld centerline (+σL up to 600 MPa) and balanced by compressive stresses further away (-σL up to -300 MPa).

[0153] For a substrate with dimensions of 635mm × 190mm × 9.5mm (L × W × T), after applying thermally induced substrate pre-bending, the substrate deflects h along the nominal substrate deflection in the z-direction. sub (bow-shaped)(h) sub =z max -z min It can be 15mm. This is a measurement that has also been verified through modeling. The substrate length is greater than L. r It is the ratio between the new x-size of the substrate Li and the substrate length L0 of 635 mm. The predicted maximum substrate deflection h. Lr Approximately deflected h from the nominal substrate sub The ratio of substrate length to L r The product of the squares of L is proportional. r Calculate using the following formula:

[0154] L r =Li / L0

[0155] And therefore

[0156] h Lr ≈h sub ×Lr 2 .

[0157] As an example, after applying thermally induced substrate pre-bending, a substrate length ratio of 3 is expected (i.e., L). r =1905 / 635=3) The longer substrate dimension is bent 15×3 2 =135mm. Therefore, the amount of substrate deflection can depend on the substrate characteristics. The longer the substrate, the higher / greater the deflection will need to be.

[0158] The heat source used to provide thermal energy to create a melt trajectory on the back side of the substrate can be any energy source capable of delivering sufficient thermal energy to melt the substrate at the heat application area to form a melt trajectory. Exemplary heat sources that can be used include arc plasma, laser beams, electron beams, and any combination thereof. In some configurations, two or more melting tools that provide individual heat sources can be used. For example, one melting tool that provides a heat source can be used to preheat the substrate, and a second melting tool that provides a heat source can be used to melt the preheated substrate to form a melt trajectory. When multiple melting tools that provide individual heat sources are used, they can be the same or they can be different from each other. Example combinations of multiple melting tools that provide DED heat sources include two PTA torches that generate arc plasma, two laser devices that generate laser beams, two electron beam devices that generate electron beams, a PTA torch that generates arc plasma and a laser heat source that generates laser beams, a PTA torch that generates arc plasma and an electron beam heat source that generates electron beams, and a laser device that generates electron beams and an electron beam device that generates electron beams.

[0159] Sufficient heat can be applied to the substrate surface to heat the substrate, thereby melting at least a portion of the substrate at the heat application area to form a melt track. The target temperature transferred by the heat source can be the melting temperature of the substrate material, or a temperature 5°C–50°C higher than the melting temperature of the substrate, or a temperature 10°C–20°C higher than the melting temperature of the substrate. Local heating of the substrate helps to induce stress in the substrate to produce a high-stress substrate in an elastoplastic state, and when the substrate is released from the fixture, the substrate bends to form a pre-bent substrate to stabilize or balance the residual stress applied by the pre-bending step. The highest stress is typically induced at the melt track, where the tensile stress peaks at the centerline of the melt track. The peak residual tensile stress can approach the yield strength of the material. As the distance from the centerline increases, the residual stress becomes compressive stress. Whether sufficient stress has been induced can be observed by observing the amount of upward displacement (i.e., bowing). The greater the displacement, the higher the residual stress introduced during pre-bending. For most substrates, the maximum residual tensile stress is close to the yield strength of the base material. The positions of these melting trajectories relative to the DED sequence can be changed to achieve a redistribution of the target residual stress.

[0160] The amount of heat required to induce the target stress and the number of melt tracks generated on the back side of the substrate can be experimentally determined. For example, an object can be produced on a first substrate using a DED without pre-bending the first substrate, and the distortion generated in the substrate can be measured. A second substrate with similar properties to the first substrate can then be pre-bent by forming melt tracks on the back side of the second substrate that fully or partially compensate for the amount of distortion measured in the first substrate. The amount of heat required to induce the target stress and the number of melt tracks generated on the back side of the substrate can also be determined based on modeling predictions, modeling, calculations, or a combination thereof. Modeling can be used to, for example, predict the development of distortion and residual stress in the substrate, and experiments can be used to confirm the modeling predictions. Simulations have also been found to be in excellent agreement with experimental data. In some embodiments, in addition to pre-defined melt tracks placed from approximately 10 mm to approximately 20 mm from the centerline of the preform, melt tracks can also be generated along the longest substrate length on parts with high aspect ratios. Assuming a square and relatively symmetrical preform shape will be produced on a square substrate, a cross-shaped pre-bending thermal application pattern on the underside of the substrate can be used to induce bending in both the longitudinal and transverse directions. As a result, the clamping mold can take on a dome shape.

[0161] After formation, the pre-bent substrate can be processed in the same manner as a conventional substrate. For consistency, the pre-bent substrate temperature can be selected, and the same temperature can be used to form similar preforms. When used and secured to a fixture, the temperature of the pre-bent substrate can be room temperature. When used and secured to a fixture, the temperature of the pre-bent substrate can be 50°C or higher. In a typical additive manufacturing process, the number of substrates required to manufacture a target number of preforms can be determined, and a sufficient number of pre-bent substrates can be produced one after another, and then each can be individually secured to a fixture at a target temperature (e.g., room temperature).

[0162] 2. Secure the pre-bent substrate to the fixture.

[0163] After pre-bending the substrate, the pre-bent substrate can be attached to a fixture or welding station. The pre-bent substrate can be attached to the fixture, for example, using clamps attached to the fixture. A bending clamping die can be used as a lower support between the pre-bent substrate and the fixture. The pre-bent substrate can have the same curvature as the bending clamping die. The pre-bent substrate can also have a different curvature than the bending clamping die. The pre-bent substrate can be positioned such that the rear side with the melt trajectory can contact the bent surface of the bending clamping die. The clamps attached to the fixture can apply force to the pre-bent substrate to cause elastic deformation of the pre-bent substrate. The clamps can force the pre-bent substrate to conform to the curvature of the bending clamping die. The clamps can be made of high-strength steel, ultra-high-strength steel, or high-strength low-alloy steel.

[0164] As clamping proceeds to secure the pre-bent substrate to the fixture, the curvature of the pre-bent substrate can gradually become similar to the curvature of the bending clamping die, and clamping can cause the curvature of the pre-bent substrate to be the same as the maximum deflection of the bending clamping die. The clamp can apply sufficient force to ensure that the surface of the pre-bent substrate makes full contact with the bent surface of the bending clamping die. Thicker substrates can provide greater resistance, thus requiring the clamp to apply greater force to overcome the elastic reaction force of the pre-bending so that the pre-bent substrate conforms to the bending clamping die. The amount of force required for the clamp to attach the pre-bent substrate to the fixture and to contact the pre-bent substrate with the underlying bending clamping support can be from approximately 10 Nm to approximately 120 Nm. For example, for a Ti-6Al-4V substrate with a thickness of approximately 9.5 mm–10 mm, the clamp can apply only 40 Nm of torque to attach the pre-bent substrate to the fixture and conform the pre-bent substrate to the bending clamping die.

[0165] Torque can be applied to the clamps to apply an initial tightening force to the substrate, followed by an additional torque to apply a final torque. Initial tightening can be achieved by sequentially tightening the clamps or by tightening clamps positioned relative to each other. The curvature of the pre-bent substrate can gradually become similar to the curvature of the bending clamping die. Upon application of the final torque, the pre-bent substrate can achieve full contact with the bending clamping die. Upon application of the final torque, the pre-bent substrate can achieve approximately 95% to approximately 100% contact with the bending clamping die.

[0166] A pre-bent substrate can be attached to a bending clamping die to ensure complete contact, for example, approximately 95% to approximately 100%, with the curved surface of the bending clamping die to achieve consistent thermal and mechanical conditions at the interface between the pre-bent substrate and the bending clamping die. Due to the curvature of the bending clamping die, a significantly smaller torque needs to be applied to the substrate via the clamp compared to the torque required to attach the pre-bent substrate flat to the clamp without the bending clamping die. The curvature of the die can be simulated by plate boundary conditions. Complete contact between the substrate and the bending clamping die is a good indicator of satisfactory clamping. To achieve satisfactory clamping, (a) a consistent clamping force can be used by applying torque-controlled tightening of the bolts attaching the clamps; (b) a consistent size can be selected from the clamps; (c) the clamping can be applied symmetrically; (d) a uniform distribution of pressure and heat transfer can be ensured by proper attachment of the clamps to avoid gaps and uneven pressure application; or (e) any combination of (a) to (d). For example, the clip can be attached to the substrate via a countersunk screw flush with the top surface of the clip to ensure uniform distribution between the clip and the substrate. The bottom and side contact surfaces of the clip can be configured and positioned such that they are flush with and in contact with the substrate to ensure uniform pressure and uniform heat transfer distribution. See, for example... Figure 14A and Figure 14B . Figure 14A The dashed circles 544, 545, 546, 547, 548, and 549 in the figure show areas of uneven pressure and heat transfer distribution due to the way the countersunk screw 510 and bolt 520, adjusted via nut 525, adjust the clamp 500 to attach the substrate 550 to the surface 530 of the clamp. In the illustration, the substrate 550 is insulated from the surface 530 of the clamp by multilayer alumina insulating plates 540 to 543.

[0167] To avoid uneven pressure and heat transfer distribution, the adjustable countersunk screw 510 is made so that the tip 515 of the countersunk screw 510 is flush with the top surface 507 of the clip 500, such as... Figure 14B As shown. This results in a uniform distribution of pressure and heat transfer. Figure 14ABoxes 575, 576, 577, and 578 illustrate areas of uniform pressure and heat transfer distribution achieved by adjusting the clamp 500 to attach the substrate 550 to the fixture surface 530 via the countersunk screw 510 and the bolt 520 adjusted via the nut 525. The illustrated embodiment shows the bottom contact surface 505 and the side contact surface 507 of the clamp 500 flush with the top and side surfaces of the substrate, respectively, to ensure uniform pressure and heat transfer distribution.

[0168] When a bending clamping die is used as a lower support to attach a pre-bent substrate to a fixture, a slight redistribution of longitudinal residual stress may occur. For example, the peak value of +σL tensile stress at the weld centerline may increase from approximately 600 MPa to approximately 700 MPa, while the -σL compressive stress away from the centerline may decrease from approximately -300 MPa to approximately -200 MPa.

[0169] Clamping the pre-bent substrate into the bending die can occur in an elastic mode. If the substrate is then released from the bending die, the curvature applied by clamping the substrate into the die can be completely reversible. This is especially true for substrates made of metals with high resilience at room temperature. The elastic deformation applied by the force of the clamp can be distinguished from the plastic deformation introduced into the substrate through the pre-bending step.

[0170] Clamps used to hold substrates to fixtures or welding stations are typically made of materials exhibiting high strength and low deformability. Steel is a suitable material for clamps due to its high strength, thermal stability, and resistance to deformation. Steel can often have a higher thermal conductivity than the substrate. For many substrates, the heat transfer in the steel within the clamp can be several orders of magnitude higher than that of the substrate. This difference in thermal conductivity between the clamp and the substrate can cause the clamp to function as a heat sink. As a heat sink, the clamp, in direct contact with the substrate during the DED process, can cause heat to flow rapidly from the area of ​​the substrate adjacent to or near the attachment point to the clamp to the clamp, and then rapidly from the clamp to the fixture or welding station. This can result in a high thermal gradient in the pre-bent substrate during the DED process. During the deposition process, this high thermal gradient can impose stress and distortion on the substrate.

[0171] To mitigate or prevent thermal gradients caused by the clip acting as a heat sink, the clip can be thermally insulating. Thermal insulation mitigates or prevents heat transfer from the substrate through the clip to the fixture. An insulating coating can be applied to all surfaces of the clip that come into contact with the substrate. The insulating coating can be any coating that does not effectively transfer heat. The insulating coating can be made of ceramic materials, silicon carbide, silicon nitride, boron carbide, or any combination thereof. Ceramic materials can be or include alumina, zirconium oxide, titanium oxide, alkaline earth metal silicates, aluminum titanate, zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, ZrV₂O₇, Mg₃(VO₄)₂, or combinations thereof. Any high-temperature ceramic coating known in the art can be used (e.g., see U.S. Patents 4,321,310 (Ulion et al., 1982), 5,789,330 (Kondo et al., 1998), 5,304,519 (Jackson et al., 1994); 6,387,539 (Subramanian, 2002); and 6,998,064 (Gadow et al., 2006). Zirconia-coated clips stabilized by the addition of yttrium oxide, such as plasma-sprayed ZrO2·8Y2O3, can be utilized. The insulating coating may comprise multiple layers of different types of ceramics, carbides, or nitrides, or combinations thereof, or multiple layers of one type of ceramic, carbide, nitride, or combination thereof.

[0172] Many of these materials are commercially available and can be applied using a variety of techniques known in the art. For example, any process can be used to apply an insulating coating, including atmospheric plasma spraying, magnetron sputtering, chemical or electrochemical deposition (e.g., electrophoretic deposition), or physical vapor deposition (e.g., electron beam physical vapor deposition), or any combination thereof.

[0173] The thickness of the insulating coating applied to the clip can vary depending on the type of insulating material used and its ability to support the load without being damaged by the applied compressive force. In some constructions, the thickness of the insulating coating can be 0.1 mm to 5 mm, or 0.25 mm to 4 mm, or 0.3 mm to 3 mm, 0.4 mm to 2 mm, or 0.5 mm to 1.5 mm. The insulating coating can be at least 0.1 mm, or at least 0.25 mm, or at least 0.5 mm, or at least 0.75 mm, or at least 1 mm, or at least 1.25 mm, or at least 1.5 mm, or at least 2.0 mm, or at least 2.5 mm, or at least 3.0 mm, or at least 3.5 mm, or at least 4.0 mm, or at least 4.5 mm. The insulating coating can have a thickness of 0.1 mm, or 0.25 mm, or 0.5 mm, or 0.75 mm, or 1 mm, or 1.25 mm, or 1.5 mm, or 2.0 mm, or 2.5 mm, or 3.0 mm, or 3.5 mm, or 4.0 mm, or 4.5 mm, or 5 mm. The insulating coating reduces heat transfer from the DED substrate to the clamp, thereby reducing heat loss from the DED substrate. An example of an insulating coating is 0.5 mm to 1.5 mm of ZrO2·8Y2O3 plasma, which is sprayed onto the contact surface of the clamp to help reduce conductive heat transfer from the DED substrate to the clamp. This provides increased thermal insulation and lower thermal conductivity.

[0174] To further reduce heat transfer from the substrate through the clip to the clamp, the thermally contacting surface of the clip can be modified to have a knurled pattern. Knurling reduces the amount of surface area of ​​the clip in contact with the substrate. Knurling reduces the chance of heat conduction between the clip and the substrate. Any knurling pattern known in the art can be used on the substrate-contacting surface of the clip. Exemplary knurling patterns include angled patterns, such as diagonal patterns, straight line patterns, diamond patterns, or any combination thereof. The knurled pattern may also have an insulating coating on its surface.

[0175] To reduce heat transfer from the substrate through the clip to the clamp, the surface of the clip in thermal communication with the substrate can be modified to have a corrugated surface including a series of ridges and grooves. The corrugated surface reduces the amount of clip in contact with the substrate. The corrugated surface reduces the chance of heat conduction between the clip and the substrate. Any corrugated pattern known in the art can be used. The corrugations can be in any direction on the surface of the clip. Exemplary configurations include angled patterns, such as diagonal corrugations, straight corrugations parallel to the long edges, straight corrugations parallel to the short edges, or any combination thereof. The corrugated surface may also have an insulating coating on its surface.

[0176] Due to limitations in coating technology, it may be more difficult to achieve thicker insulating coatings capable of withstanding the compressive forces necessary to secure a pre-bent substrate to a clamp. The specific compressive strength of an insulating coating can be determined by its composition. For example, it has been found that 0.5 to 2.0 mm thick coatings of zirconium dioxide-based ceramics stabilized by the addition of yttrium oxide provide good thermal insulation and good compressive strength when attaching a substrate to a clamp using clips, without damaging the insulating coating.

[0177] Figure 9A , Figure 9B and Figure 9C An exemplary construction of the clip is shown in the figure. Figure 9A A bottom view of a clip 500 with a threaded hole 501 for receiving a countersunk screw and a hole 502 for receiving a bolt is shown. The top surface 507 may include a ceramic-coated surface 509 at the edge that will contact the substrate. The top surface 507 may be corrugated. Figure 9B A side view of the clip 500 is shown, which shows the ceramic-coated surface 509 of the bottom contact surface 505 and the side contact surface 506 that are in contact with the substrate. Figure 9C An oblique top view of a three-dimensional view of clip 500 is shown, illustrating the threaded hole 501 of clip 500 and the ceramic-coated bottom contact surface 505 and side contact surfaces 506. Clips with the same design can be used (e.g., all clips have the same length, or the same width, or the same length and width). Clips with different lengths and / or widths can also be used.

[0178] Thermally insulating clips can be positioned around the entire periphery of the pre-bent substrate to ensure complete contact between the pre-bent substrate and the bending clamping die, for example, approximately 95% to approximately 100% contact. An exception to using only insulating clips would be when a PTA welding torch is used as a DED melting tool to provide arc plasma as a heat source. In this configuration, one or more non-insulating clips can be used to provide a current path. For example, in an exemplary configuration, two or three non-insulating clips can be used to ensure a stable current path from the power source. In this configuration, one or two non-insulating clips can be positioned on the short edge of the substrate, and one non-insulating clip can be positioned at the midpoint of the longest substrate dimension. Other configurations can be used.

[0179] To mitigate stress and distortion in the substrate during metal deposition and object fabrication, the clips can be positioned onto the substrate by intersecting the centerlines of the clips at the start / end points of the DED lines / walls wherever possible. Figure 10An exemplary configuration is shown. In the illustrated configuration, clamps 500 are positioned around preform 600 such that nearly all periphery of substrate 300 is clamped to fixture 400, positioned such that the centerline of clamp 500 intersects, wherever possible, the centerline of the start / end position of the DED line / wall of preform 600 (shown as clamping entities 610, 615, 620, 625, and 630). These substrate clamping constraints significantly reduce the deformation effects during deposition primarily caused by longitudinal residual stress. Suboptimal clamping can produce localized deformation or buckling due to a lack of clamping constraints, as shown in the dashed outline 650.

[0180] Different clamping devices can be used during the pre-bending and attachment of the pre-bent substrate to the fixture for DED processing. The choice of clamping devices is possible because during pre-bending, applying heat to the rear side of the substrate using a melting tool that provides the DED heat source may require increased proximity of the heat source to the full or near-full length of the substrate to produce a uniform deflection along the longest length of the substrate. Insulating clamps may not be used at the edges so that the melting tool providing the DED heat source can apply heat to the full length of the substrate. During the construction of the object by metal deposition on the front side of the substrate, insulating clamps may be placed around the perimeter of the substrate, particularly at the beginning / end positions of the DED walls, to help reduce localized deformation caused by the development of residual stress. The clamping configuration can (1) promote symmetry on the board, (2) utilize clamps with the same geometry when possible, (3) allow desired proximity to the substrate by the melting tool providing the DED heat source, and (4) meet the torque requirements necessary to attach the pre-bent substrate to the fixture.

[0181] Using a bending clamping die can significantly improve the manufacturing process, but it is possible to perform a DED process on the front side of a pre-bent substrate by using an insulating material sheet, such as a conventional alumina (Al2O3) insulating sheet or plate, which is cut to form a curvature that roughly matches the arc of the pre-bent substrate. This is significantly more labor-intensive than using the bending clamping die provided herein. Furthermore, part-to-part variations can occur due to variations in the thickness of the alumina insulating plate and the formation of layers of pre-cut sheets that match the curvature of the pre-bent substrate. The bending clamping die provided herein can mitigate or prevent such part-to-part variations by providing a die with consistent physical and mechanical properties that allow for multiple uses.

[0182] 3. Preheating the substrate

[0183] Once the pre-bent substrate has been secured to the fixture using a bending clamping die and insulating clips, it can be preheated before starting the DED process. The preheating step aims to treat most of the front surface of the substrate with a heat source to uniformly heat the substrate as a whole to the target temperature, after which the DED process is used to build the workpiece while the pre-bent substrate is still hot.

[0184] In contrast to the application of energy to the back side of the substrate in the pre-bending step (where a steep thermal gradient and high cooling rate are chosen to generate higher internal tensile and compressive stresses), energy is delivered towards the front side of the substrate in a more gradual and uniform manner during the preheating step. During the preheating step, energy can be directed to the front side of the substrate using a heat source without locally melting the substrate surface. During the preheating step, energy can be directed to the front side of the substrate using a heat source without forming a continuous melt path. Because near-uniform heating is desired, the energy from the heat source allows for a relatively low rate of application of the melting tool, and the melting tool is positioned at a greater spacing (further away from the substrate) to apply heat at a lower energy density. Additionally, because the preheating step aims to heat the substrate before building the workpiece using the DED process, a gas jet is not used to apply cooling gas. Therefore, the cooling rate is significantly lower than that that can occur in the pre-bending step.

[0185] This slower heating / cooling cycle during preheating promotes a slower cooling rate and the formation of low thermal gradients along the x, y, and z directions in the substrate. Applying energy during preheating allows for a slow accumulation of residual heat, as heat can be dissipated throughout the pre-bent substrate volume via conduction. For example, a lower thermal gradient can be delivered to the substrate at a lower energy density. These conditions can create a “near” uniform temperature distribution on the substrate, allowing residual heat to accumulate slowly as it dissipates throughout the substrate volume via conduction. Because the pre-bent substrate is thermally insulated from the bending clamping die and is secured to the clamp using insulating clamps, residual heat is more easily retained within the substrate.

[0186] Low energy density can be delivered to the substrate continuously to create a near-uniform temperature distribution across the substrate surface and throughout its thickness. To avoid exposing any region to accumulated heat, energy application can begin at a first edge of the substrate and continue along the X-direction across the substrate surface until it reaches the opposite second edge. The melting tool, providing the heat source, can then move back to the first edge and reposition itself in the Y-direction, a distance from the initial energy application, and apply energy along the X-direction. This process is repeated until the pre-bent substrate has reached the target temperature. A more uniform temperature distribution within the substrate is beneficial for mitigating stress and distortion effects occurring within the substrate.

[0187] exist Figure 11 The diagram illustrates an exemplary pattern used for energy application during preheating. Light black arrows indicate the direction / path of the DED energy source, including the X... ES The circles indicate a sequence X, where X is 1 to 8 on the surface of the second side 320 of the substrate 300, where S indicates the start of the path and E indicates the end of the energy application path, thus creating a heating path. In the pattern shown, heating occurs at the bottom edge (1) across the x-direction. ES ) Start, then the heat source moves in the y-direction to a point approximately one-ninth of the way up from the initial heating path, and heat is applied in the y-direction from the short edge to the short edge (2 ES ). For 3 ES 4 ES , 5 ES 6 ES , 7 ES and 8 ES Repeat this process until heat has been applied to the surface of substrate 300. The first heating path 700 corresponds to 1. ES The second heating path 705 corresponds to 2. ES The third heating path 710 corresponds to 3. ES The fourth heating path 715 corresponds to 4. ES The fifth heating path 720 corresponds to 5. ES The sixth heating path 725 corresponds to 6. ES The seventh heating path 730 corresponds to 7. ES The eighth heating path 735 corresponds to 8. ESA single energy source or multiple energy sources can be used in the preheating path. The diagram shows solid lines and light black dashed lines representing the tool paths and preheating sequence of two parallel melting tools. While the illustrated embodiment describes heating using DED energy, other energy sources can be used. Exemplary alternative energy sources include, for example, one or more lasers, one or more induction heaters, or any combination of a laser, DED energy, and an induction heater. Additionally, other methods and apparatus that enable uniform heating of the substrate can also be used, such as induction heating, resistance heating, etc.

[0188] The preheating direction can be the same as the actual DED process for forming the preform, so that the temperature and residence time in the region below the DED deposition area can be similar. For example, as Figure 11 As shown, during the DED process, the start (S) and end (E) positions of the preheating thermal energy application (as indicated by the light black arrows, and each marked with a circle) are in the same metal deposition direction.

[0189] Heat application can be performed using any source that generates heat. For example, arc-based laser beams and electron beam heat sources can be used alone or in combination to achieve a preheating effect. For instance, one or more thermoelectric welding sources, such as a preheating PTA torch and a melting PTA torch, can be positioned laterally across the substrate to heat it. The PTA torch can be positioned to mitigate temperature gradient formation and reduce the total preheating time. Other heat sources based on laser or electron beam energy can also be used for the same purpose, but with a suitable set of parameters to achieve similar heating of the substrate. The spacing between preheating heat application areas can depend on the amount of heat delivered by the heat source.

[0190] For example, two PTA thermoelectric plasma welding torches can be used simultaneously, laterally, to heat a substrate. The two torches can have a fixed distance between them, for example, approximately 20 mm to 40 mm. This configuration applies heat energy along the x-direction and across the y-direction in such a way that heat is delivered and diffused as uniformly as possible without overlapping with the centerline of the heat source. On the other hand, for a fixed substrate width, the amount of preheating can differ if a more concentrated heat source, such as laser energy or electron beam energy, is used for this purpose. The laser or electron beam spot can be designed to be larger to achieve a wider heating area on the substrate. Other methods and apparatus that enable uniform heating of the substrate include induction heaters and resistance heaters.

[0191] A melting tool providing the DED heat source can be used to perform uniform preheating. The positioning, sequence, and parameters used to perform preheating with the melting tool providing the DED heat source can be controlled such that applying energy to the substrate results in a lower thermal gradient generation than that applied to the substrate during the pre-bending step. Preheating can be performed to uniformly raise the temperature of the substrate. In an exemplary embodiment, depending on the substrate material, preheating can be performed to uniformly raise the temperature of the substrate to a temperature in the range of approximately 350°C to approximately 650°C. For example, a Ti-containing substrate can be preheated to a temperature in the range of approximately 400°C to approximately 550°C. For some Ti alloys, the substrate can be preheated to a temperature in the range of approximately 450°C to approximately 500°C to mitigate thermal gradient formation during DED. Preheating can mitigate internal stress accumulation during DED processing by reducing any localized stress caused by heating during the deposition of molten metal to build the workpiece. By preheating the substrate to an elevated temperature, such as a warm-formation temperature or thermal-formation temperature, preparing solder beads on the substrate during DED workpiece formation can result in near-zero distortion because the resulting thermal gradient is significantly smaller than the thermal gradient generated through thickness when the solder is deposited onto the substrate at room temperature. Preheating is not intended to significantly alter or melt the substrate surface, but rather to result in the formation of solder lines without adding any metal.

[0192] Indirect heating (e.g., heating a pre-bent substrate clamped to a fixture in an oven to uniformly raise the substrate temperature) can be used for preheating. In some applications, this is not feasible or practical. The time required to move the substrate / fixture assembly from the oven to the chamber where DED processing can be performed can result in significant loss of residual heat from the substrate, thus negating the purpose of the preheating step. The system can be modified to include an oven accessible via the deposition chamber to allow for oven-based preheating of the substrate.

[0193] Direct heating can be used, employing a heating device positioned to apply heat to the surface of the substrate when it is attached to a fixture. Any method and heating device that enables uniform heating of the substrate prior to deposition can be used. The heating device can be or includes an induction heater, a resistance heater, or a combination thereof. Exemplary heaters include a conductor heat source within a conduit, a heater bar, a resistance heating bar, an infrared heater, a positive thermal coefficient ceramic heater, a thick-film ceramic heater, a resistance wire or resistance strip heating device, and induction heaters and heaters that may include any combination thereof.

[0194] 4. DED process for constructing workpieces

[0195] After the substrate is preheated to the target temperature, the DED process can be performed immediately to form the workpiece on the substrate. During the construction of the object by depositing metal on the front side of the substrate, clips can typically be positioned at the start / end of the DED wall to help reduce localized deformation caused by the development of residual stress.

[0196] Before preheating, the pre-bent substrate can be in full contact with the bending clamping die via insulating / non-insulating clamps attached to the fixture, for example, approximately 95% to approximately 100% contact. The substrate can be thermally separated from the fixture by the bending clamping die. The bending clamping die may include an insulating ceramic layer on its bent surface that can contact the pre-bent substrate. The pre-bent substrate is not bonded to the bending clamping member. Furthermore, as can be seen from this arrangement, while the pre-bent substrate is secured to the fixture, the workpiece can be built onto the surface of the pre-bent substrate. Although the pre-bent substrate can become part of the workpiece, no part of the bending clamping die becomes part of the workpiece.

[0197] Although the pre-bent substrate has an arcuate shape and is attached to a curved clamping member that also has an arcuate shape, the slope of the curve of the pre-bent substrate, which is fixed to the fixture by the curved clamping member, does not affect the overall deposition conditions, where the curved clamping member acts as a support between the pre-bent substrate and the fixture. The radius of curvature of the curved clamping die is large enough that the effects of gravity do not adversely affect the molten pool dynamics, allowing deposition on the pre-bent substrate in contact with the curved clamping die to be similar to deposition achieved if it were deposited in a flat location on the substrate. The radius of curvature of the curved clamping die can be selected such that the effect of gravity caused by this slope does not affect the behavior of the liquid molten pool deposited or formed on the surface of the pre-bent substrate. Furthermore, the controller used to build the workpiece in the DED process can adapt the z-coordinate to the curvature of the curved clamping die to ensure that the DED process delivers consistent energy / processing conditions during workpiece manufacturing. Executable CAD-CAM program instructions cause the melting tool to provide a DED heat source that follows the precise shape of the curved clamping die to ensure that overall processing conditions, especially distances, are unaffected.

[0198] The design of a workpiece constructed using the DED process can be positioned on the front side of the substrate such that a large portion of the workpiece wall, formed by the deposition of molten metal, lies between adjacent melt tracks on the rear side of the substrate, preferably equidistant from these adjacent melt tracks. This positioning allows for the relocation of areas prone to uneven plastic deformation and high tensile stress during DED fabrication that may occur in the molten region, to areas of high compressive stress imposed by the pre-bending process, and for the relocation of compressive stress that may form as the weld seam cools, to areas of high tensile stress imposed by the pre-bending process. Therefore, since the workpiece wall is positioned on the front side of the substrate relative to the melt tracks on the rear side, the residual stress field is balanced, thereby mitigating the overall distortion in the deposited preform.

[0199] Figure 11 An exemplary deposition pattern for forming a preform is shown. As shown, the preform 600 is located on the front or second side 320 of the substrate 300, such that most of the walls (e.g., 380, 382, ​​and 384) of the workpiece preform 600 formed by the deposition of molten metal are located between, and preferably equidistant from, adjacent preheating paths 700, 705, 710, 715, 720, 725, 730, and 735 on the rear or first side 310 of the substrate 300. The exemplary DED sequence paths for each layer are indicated sequentially by boxes S1 to S5, where arrows indicate the DED direction for each layer.

[0200] In the method for producing metal workpieces using the DED process provided herein, a three-dimensional object of metallic material is fabricated by fusing a continuous deposit of metallic material together onto a substrate. Any DED process can be used to construct the workpiece. The DED process can use one or more melting tools that provide an energy source, either individually or in combination. Exemplary melting tools that can be used include PTA torches that provide an arc plasma as a heat source, laser devices that provide a laser beam as a heat source, electron beam devices that provide an electron beam as a heat source, and any combination thereof. In some constructions, two or more melting tools that provide heat sources can be used. For example, a melting tool that provides a DED heat source can be used to preheat a substrate, and a second melting tool that provides a DED heat source can be used to melt metallic material to form molten metal that can be deposited on a preheated region. When multiple melting tools that provide DED heat sources are used, they can be the same or they can be different from each other. Exemplary combinations of multiple melting tools include two PTA torches, two laser beam devices, two electron beam devices, a PTA torch and a laser beam device, a PTA torch and an electron beam device, and a laser beam device and an electron beam device.

[0201] In some methods, a first melting tool can be used to deliver energy to at least a portion of the surface of the base material, such as at the location where the metal material will be deposited, for surface heating of the substrate. This differs from a preheating step, which is used to raise the temperature of the entire substrate to a target temperature to minimize thermal gradients during the DED process. Instead, for surface heating of the base material, whether the base material is a substrate or a previously deposited metal layer, the first melting tool delivers high-intensity energy to a limited area of ​​the base material, thereby raising the temperature of the base material at the energy application area to a temperature slightly below the melting temperature, for example, 0.1% to 10% lower, or to the melting temperature. Surface heating of the base material can improve weld wetting and spread characteristics. Surface heating of the base material can improve the weld bead contact angle. Surface heating of the base material can make the surface more receptive to molten metal to be deposited on the heated surface.

[0202] The second melting tool can be used to heat and melt metallic materials, causing the molten metal to deposit onto a heated surface area of ​​the base material heated by the first melting tool. A gas jetting device can be used to guide cooling gas through the surface of the molten pool, or to impinge on the surface of the molten pool, or on the surface of the solidified material at the liquid-solid boundary adjacent to the molten pool, or any combination thereof. The base material can be moved in a predetermined pattern relative to the positions of the first and second melting tools and the gas jetting device, causing a continuous deposit of molten metal to solidify and form a three-dimensional workpiece. Alternatively, the first and second melting tools and the gas jetting device can be moved in a predetermined pattern relative to the position of the base material, causing a continuous deposit of molten metal to solidify and form a three-dimensional workpiece.

[0203] In the method provided herein, the cooling gas can be or includes an inert gas, such as argon, helium, neon, xenon, krypton, or combinations thereof. The cooling gas can have a flow rate from approximately 1 L / min to approximately 300 L / min, measured at the inlet. The cooling gas can be applied at a constant flow, intermittently, or pulsed. The flow of the cooling gas can be adjusted to generate turbulence near the molten pool. For example, the velocity of the cooling gas flowing through the gas jet device can be increased so that the cooling gas exiting the gas jet device exhibits turbulence rather than laminar flow. The cooling gas can be delivered using multiple nozzles on a single gas jet device or using multiple gas jet devices, such that a combination of laminar and turbulent flow of the cooling gas can be directed towards the vicinity of the molten pool.

[0204] The applied cooling gas can be at any temperature. The cooling gas temperature can be the ambient temperature of the chamber in which the additive forming process is performed. The cooling gas temperature can be approximately room temperature or lower, such as approximately 25°C or lower. The cooling gas can be at a refrigerated temperature, such as 150°C to approximately 4°C, or approximately -10°C to approximately 10°C.

[0205] The number and configuration of the nozzles of the gas jet device, and / or the number of gas jet devices, and their configuration and placement, may be selected to deliver cooling gas covering the length of the workpiece, such as a distance along the direction of travel at or around the thermal impact zone, which is approximately 5 mm to approximately 50 mm, or approximately 10 mm to approximately 40 mm, or approximately 15 mm to approximately 30 mm.

[0206] In the method presented herein, the melting tool providing the DED heat source can be used in combination with a gas jetting device to control the molten pool conditions, wherein the gas jetting device generates cooling gas, resulting in a temperature reduction of approximately 1200°C to approximately 600°C or approximately 1000°C to approximately 800°C. In some methods where the workpiece is formed from a Ti alloy, a temperature reduction of 1000°C to 800°C can be used.

[0207] The method described herein can be performed in any additive manufacturing system. This method can be performed in systems where an inert gas surrounds only a heat source, such as an electric arc plasma, or a melting tool containing a heat source, or both the melting tool and the workpiece. The method can be performed in systems comprising a closed chamber filled with an inert gas to provide an inert atmosphere, wherein the entire process is performed within an inert atmosphere. The inert atmosphere can be or contains argon, xenon, neon, krypton, helium, or combinations thereof, allowing for inert atmosphere deposition.

[0208] Figure 12A and Figure 12B The diagram illustrates an exemplary difference between a conventional substrate construction for the DED process and a process provided herein using a bent clamping die. Figure 12A A conventional configuration is shown, in which a substrate 300 (via clips, not shown) is secured to a fixture 400, but is thermally insulated from the fixture 400 by alumina insulating plates 540, 541, 542, and 543 positioned between the substrate 300 and the fixture 400. The substrate 300, which has not undergone any stress-relief treatment, is flat, and metallic material is deposited on the upper surface of the substrate 300 during the DED process to produce preforms 600 and 600'.

[0209] on the contrary, Figure 12B An exemplary embodiment of a substrate configuration using a bending clamping die 100 with a knurled or corrugated surface (not shown) coated with a ceramic coating 150 is illustrated. In the illustrated configuration, the bending clamping die 100 serves as a lower support for the substrate 300 when the substrate 300 (via a clamp, not shown) is secured to the fixture 400. The bending clamping die 100 eliminates the need for any alumina insulating plates or other substrate support devices typically used for thermally separating the substrate from the fixture, as the bending clamping die 100 thermally insulates the substrate 300 from the fixture 400. The substrate 300 can undergo the stress relief process disclosed herein, resulting in pre-bending of the substrate 300. The pre-bent substrate 300 can be clamped to the bending clamping die 100 using insulating clamps (not shown). The curves shown are exaggerated; the radius of curvature of the bending clamping die 100 is large enough that the effects of gravity do not adversely affect the molten pool dynamics, making the deposition resemble deposition achieved as if in a flat position. During the DED process, metallic material is deposited on the upper surface of substrate 300 to produce preforms 600 and 600'.

[0210] D. System

[0211] A system for constructing metal workpieces using a DED process is also provided. This system may include a fixture for securing a pre-bent substrate to it; a bending clamping die that serves as a lower support for the pre-bent substrate when it is secured to the fixture; an insulating clamp for securing the pre-bent substrate to the fixture; one or more melting tools, including a DED energy source, to melt a metal source into a molten metal material that can be deposited onto the surface of a base material (for the first layer, the base material will be the surface of the substrate; for subsequent layers, the base material will be the surface of the previously deposited metal layer); and a gas jetting device for guiding cooling gas through, impacting, or striking the molten pool. The workpiece is formed by striking a solidified material adjacent to the liquid-solid boundary of a molten pool, or any combination thereof; a cooling gas supply device; a system for positioning and moving a base material relative to a melting tool and a gas jetting device; and a controller capable of reading a design model of the metal workpiece to be formed, such as a computer-aided design (CAD) model, and using the design model to adjust the position and movement of the system for positioning and moving the base material, and operating the melting tool and the gas jetting device to construct the workpiece by fusing the metal material onto the base material to form a continuous deposit of the metal material.

[0212] A single melting tool can be used, or two melting tools can be used. For example, a first preheating torch generates a single preheating arc plasma, and a second torch generates a dual-arc plasma. The two torches can be used simultaneously, one after the other. The preheating arc can transfer heat energy to a portion of the surface of the base material, for example, at the location where the metal DED material is to be deposited, for surface heating or pretreatment of the substrate. Alternatively, the dual-arc plasma can be powered by a separate power supply. The dual-arc plasma can be used to resistively heat and melt metal onto a surface-heated area of ​​the base material. The dual-arc plasma ensures adequate fusion between the base material of the workpiece and the molten metal produced by the action of the arc plasma arc on the metal (e.g., wire feedstock). For example, the second melting tool can be a torch that generates dual-arc plasma, where one arc burns between the tungsten electrode of the torch and the workpiece (PTA), while the other arc burns between the tungsten electrode of the torch and the wire feedstock (main arc), both using positive polarity. PTA arc plasma can deepen the fusion properties of molten metal into the preheated surface of the base material, which can be controlled independently of the main arc plasma. The main arc plasma can be established between the welding torch and the current-carrying wire feedstock. The wire feedstock can be melted by heat generated by the column of PTA arc plasma transferred to the workpiece and by heat generated by the main arc plasma circuit. The wire feedstock produces molten metal that can be deposited on the workpiece. Superheating from the molten metal droplets can maintain the molten pool near the surface-heated area of ​​the base material. Surface heating of the base material results in enhanced fusion, improved wetting and spreading properties of the liquid pool, and therefore better overall DED properties. Regarding deposition distribution, a shallower and wider deposition distribution can be obtained by surface-heating the substrate. Improved weld bead properties result in a distribution with a beneficial weld bead contact angle toward the base material, which promotes full fusion with the base material and adjacent weld beads. Improved weld bead and fusion properties produce manufactured products with improved mechanical integrity.

[0213] Each melting tool can be controlled independently and is therefore individually modulated to generate separate temperature and pressure fields. The advantage of this arrangement is that the amount of heat energy applied to the metal material to be melted in the surface heating zone of the base material can be greater than the amount of heat energy applied to the surface of the base material, thus preventing overheating of the base material.

[0214] The DED manufacturing system described herein may include a PTA torch, a laser device, an electron beam device, or any combination thereof as a melting tool. In some configurations, a first PTA torch electrically connected to the surface of a base material heats a target deposition area on the base material to form a surface-heated region, and a second PTA torch electrically connected to a consumable electrode heats and melts the consumable electrode, which can cause molten metal droplets to fall onto the surface-heated region of the target deposition area. In some configurations, the PTA torch can surface-heat a target deposition area on the base material to form a surface-heated region, and the laser device can heat and melt a metal wire or metal powder, which can cause molten metal to form on the surface-heated region that can be deposited onto the target deposition area. In some configurations, the PTA torch can heat a target deposition area on the base material to form a surface-heated region, and the electron beam device can heat and melt a wire, which can cause molten metal droplets to fall onto the surface-heated region of the target deposition area.

[0215] In some configurations, a laser device can point-heat a target deposition area on a base material to form a point-heated region, and a PTA welding torch electrically connected to a consumable electrode can heat and melt the consumable electrode, which can cause molten metal droplets to fall onto the point-heated region of the target deposition area. In some configurations, a first laser device can point-heat a target deposition area on a base material to form a point-heated region, and a second laser device can heat and melt a metal wire or metal powder, which can cause molten metal to form on the point-heated region of the target deposition area. In some configurations, a laser device can point-heat a target deposition area on a base material to form a point-heated region, and an electron beam device can heat and melt a metal wire, which can cause molten metal droplets to fall onto the point-heated region of the target deposition area.

[0216] In some configurations, an electron beam device can point-heat a target deposition area on a base material to form a point-heated region, and a PTA welding torch electrically connected to a consumable electrode can heat and melt the consumable electrode, causing molten metal droplets to fall onto the point-heated region of the target deposition area. In some configurations, an electron beam device can point-heat a target deposition area on a base material to form a preheated region, and a laser device can heat and melt a metal wire or metal powder, causing molten metal droplets to fall onto the point-heated region of the target deposition area. In some configurations, a first electron beam device can point-heat a target deposition area on a base material to form a point-heated region, and a second electron beam device can heat and melt a metal wire or powder, causing molten metal droplets to fall onto the point-heated region of the target deposition area.

[0217] In some configurations, the DED manufacturing system may include a laser device or a PTA torch, which may be arranged to direct energy (e.g., laser energy or plasma-transferred arc, respectively) to a target area of ​​the base material to form a surface-heated region. The PTA torch or laser device may be arranged to direct energy to the end of a consumable electrode or wire positioned above the surface-heated region of the base material. This energy can melt the end of the consumable electrode or wire, forming a molten metal droplet that can fall onto the surface-heated region of the base material below the end of the consumable electrode or wire. A melting tool that directs energy to the target deposition area can facilitate fusion between the base material and the molten metal material deposited thereon by deepening the melting of the molten metal droplet into the base material. The melting tool used to melt the consumable electrode or wire may also contribute thermal energy near the point-heated region of the target deposition area, thus contributing thermal energy directed towards the base material provided by the melting tool. Superheating from the molten metal droplet helps maintain a molten pool near the point-heated region of the base material.

[0218] The consumable electrode or wire may be or contains Al, Cr, Cu, Fe, Hf, Sn, Mn, Mo, Ni, Nb, Si, Ta, Ti, V, W, or Zr, or a composite or alloy thereof. In some embodiments, the consumable electrode may be a wire containing Ti or a Ti alloy. The consumable electrode or wire may be or contains a titanium alloy containing Ti and one or a combination of Al, V, Sn, Zr, Mo, Nb, Cr, W, Si, and Mn. For example, exemplary titanium alloys include Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-45Al-2Nb-2Cr, Ti-47Al-2W-0.5Si, Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si, and Ti-48Al-2Nb-0.7Cr-0.3Si. Consumable electrodes or wires may contain aluminum, iron, cobalt, copper, nickel, carbon, titanium, tantalum, tungsten, niobium, gold, silver, palladium, platinum, zirconium, their alloys, and combinations thereof. Consumable electrodes may include solid wire electrodes, cored wire electrodes, or strip electrodes.

[0219] The typical cross-section of a consumable electrode or wire is circular. The diameter of the consumable electrode or wire can be up to approximately 10 mm, and can range from approximately 0.8 mm to approximately 5 mm. The consumable electrode or wire can have any practically achievable cross-sectional size, such as 1.0 mm, 1.6 mm, and 2.4 mm, or approximately 0.5 to approximately 3 mm. The feed rate and positioning of the consumable electrode or wire can be controlled and adjusted based on the effect of powering the PTA welding torch, laser device, electron beam device, or any combination thereof, to ensure continuous heating and melting of the consumable electrode or wire as it reaches the intended position above the preheated zone of the base material.

[0220] The laser device can generate a laser beam of sufficient energy to transfer heat to the base material, thereby preheating the surface area of ​​the base material or melting the wire. Preheating the base material via energy from the laser beam can promote fusion between the base material and the molten metal by enhancing the melting properties of the base material. In some embodiments, at least a portion of the base material can be melted by the energy from the laser beam from the laser device. In some embodiments, the laser beam from the laser device can apply sufficient heat to form a molten pool in the base material at the location where the metal material generated by the PTA welding torch or another laser device or electron beam device will be deposited.

[0221] Examples of suitable laser devices include ytterbium (Yb) lasers, Yb fiber lasers, Yb fiber-coupled diode lasers, Yb:glass lasers, diode-pumped Yb:YAG lasers, neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, CO2 lasers, CO lasers, Nd:glass lasers, neodymium-doped yttrium orthovanadate (Nd:YVO) lasers, Cr:ruby lasers, diode-pumped lasers, excimer lasers, gas lasers, semiconductor lasers, solid-state lasers, dye lasers, X-ray lasers, free-electron lasers, ion lasers, gas mixture lasers, chemical lasers, and combinations thereof. Preferred lasers include Yb lasers, particularly Yb fiber lasers. In many applications, the wavelengths used in Yb fiber lasers have lower reflectivity compared to other laser wavelengths.

[0222] A PTA welding torch can be any construction capable of generating an arc plasma to resistively heat and melt consumable electrodes, or to heat a target area on the surface of a base material, such as gas metal arc welding (GMAW), particularly using an inert gas to establish the arc (metal inert gas welding or MIG welding). The consumable electrode can be melted in the plasma generated by the arc from the PTA welding torch, and the molten consumable electrode can be deposited into a molten pool on the workpiece to incorporate and form a near-net-shape metal body. Preheating the base material via energy from the PTA welding torch can promote fusion between the base material and the molten metal by deepening the melting properties of the base material. In some embodiments, at least a portion of the base material can be melted by the energy of the plasma from the PTA welding torch. In some embodiments, sufficient heat can be applied by the plasma from the PTA welding torch to form a molten pool in the base material at the location where the metal melted by a different PTA welding torch or laser device will be deposited.

[0223] By introducing a melting trajectory to thermally pre-bend the substrate, using a bending clamping die, and preheating the substrate before forming the workpiece using the DED process, near-net-shape metal workpieces can be formed, significantly mitigating problems associated with noticeable internal residual stress and deformation in many conventional additive manufacturing products. This results in improved manufacturing repeatability, increased dimensional accuracy, and manufactured workpieces exhibiting increased strength, fatigue resistance, and durability.

[0224] E. Example

[0225] The following examples are included for illustrative purposes only and are not intended to limit the scope of the implementations provided herein.

[0226] Example 1

[0227] A first substrate made of Ti-6Al-4V with dimensions (L×W×T) of 635mm×190mm×9.5mm was used as the first test substrate to determine the deflection without alleviating residual stress. The substrate was clamped to a jig or welding table, and the base material was preheated using a first PTA torch. A second PTA torch was used to melt the Ti-6Al-4V wire to form molten metal deposited on the preheated substrate, thereby creating a workpiece. The deposition rate was between 7.5mm / s and 10mm / s, and an inert gas was used to guide the cooling gas at a high flow rate to impinge on the solidified material at the liquid-solid boundary adjacent to the molten pool. After deposition, the part was cooled and removed from the jig, and the substrate deformation was inspected.

[0228] A noticeable distortion is observed at the short edges of the substrate, curving upwards compared to the flat profile of the substrate before deposition. The observed deformation is as follows... Figure 13A As shown.

[0229] A second test substrate was used, consisting of a second substrate with dimensions (L×W×T) of 635mm×190mm×12.7mm and made of Ti-6Al-4V. The same workpiece was fabricated under the same conditions as described above. Figure 13B The deformation resulting from DED deposition on a 12.7 mm thick substrate that has not been subjected to any type of residual stress relief is shown. Compared to the flat profile of the substrate before deposition, the deformation exhibits an upward bend at the short edges of the substrate, with the left edge bending upward by approximately 7 mm and the right edge bending upward by approximately 6.0 mm.

[0230] Figure 13CA third substrate with dimensions (L×W×T) of 635mm×190mm×9.5mm and made of Ti-6Al-4V is shown for forming an object by undergoing thermal pre-bending, preheating, and DED processes as described herein. The substrate is securely clamped to a fixture using insulating clips along its entire length, around the long edge, but not along the short edge. Four layers of alumina insulation, each approximately 3.2mm thick (RS-1200 Keranova), are used between the substrate and the fixture to thermally insulate the substrate from the fixture.

[0231] The PTA torch is used to deliver heat to the first side of the substrate to create a melt trail within the substrate. Compared to the original residual stress distribution of the DED, the final aggregated residual stress distribution determined by the combination of the DED and the melt trail has a lower tensile peak at the centerline of the DED and lower equilibrium compressive stress further away from the centerline, without the pre-bending melt trail (i.e., a high tensile peak at the centerline of the DED and lower equilibrium compressive stress further away). Figure 7A and Figure 7B The diagram illustrates a pattern used to generate melt tracks. As shown, a PTA welding torch, serving as the heat source for the DED, is positioned at one edge of the substrate. The spacing between melt tracks can be predicted based on the shape of the workpiece to be produced. For example, melt tracks can be formed in areas not below the walls of the workpiece to be formed, in order to minimize the final distribution of accumulated residual pressure in the workpiece. For example, a large portion of the melt line on the first surface can be formed at one or more locations other than those corresponding to one or more areas occupied by one or more walls of the workpiece to be formed on the second side of the substrate. To induce maximum thermal stress in the substrate, a high energy density (e.g., an arc energy delivered at approximately 450 J / mm to approximately 550 J / mm) is applied at a rate between 6 mm / s and 16 mm / s to rapidly melt a portion of the substrate surface to generate a self-generated weld line. This self-generated weld line is rapidly cooled using a gas jet device to direct cooling gas at a temperature of 25°C at a high flow rate toward the weld line, thereby forming a melt track with high tensile stress near the centerline of the melt track and high compressive stress at a distance away from the centerline. In an exemplary embodiment, for a substrate thickness of 9.5-10 mm, a single heat source with a current of approximately 150 A to approximately 250 A, a voltage of approximately 20 V to approximately 30 V, and a traverse speed of 6 mm / s to 16 mm / s is used to generate a melt track approximately 3 mm wide and at most 1 mm deep.

[0232] Upon release from the fixture, the pre-bent substrate bends upward, exhibiting a deflection of approximately 15 mm, similar to... Figure 8AThe deflection is shown. The pre-bent substrate is then attached to the fixture using a bending clamping die as a lower support and insulating clamp. The pre-bent substrate is positioned such that the side with the melt trajectory faces the bending clamping die. Preheating of the pre-bent substrate is accomplished using two PTA torches. By positioning the PTA torches at a greater distance apart, a lower energy density is delivered to the surface of the pre-bent substrate to reduce the risk of localized melt trajectories that can cause fusion problems at the substrate interface during DED metal deposition. For example, preheating is performed using two PTA torches with an arc voltage in the range of 150-250A and 20-30V. The traverse speed is between 6-12 mm / s. For example, the arc energy delivered by the first PTA torch can be 460 J / mm, and the arc energy delivered by the second PTA torch can be 430 J / mm. Another important aspect is that the pre-bending trajectory is performed using a plasma gas flow with a higher plasma gas flow than that used in preheating. A higher plasma gas flow produces a stronger electric arc, resulting in a higher energy density. Regarding the phase spacing, a spacing 25% to 50% higher, or 30% to 40% higher, can be used during preheating compared to the spacing used in pre-bending. No cooling gas is used during the preheating process.

[0233] After the substrate temperature reaches between 450°C and 550°C, DED deposition of the metal is performed in a closed chamber containing an inert argon atmosphere to form an object. The DED process uses two PTA torches. The first PTA torch directs heat energy to a target area of ​​the base material to form a preheated region, and the second PTA torch directs heat energy to (1) the end of a consumable electrode or wire positioned above the preheated region of the base material, and (2) towards the preheated region. The energy from the second PTA torch melts the end of the consumable electrode or wire, forming molten metal droplets that fall onto the preheated region of the base material below the end of the consumable electrode or wire. The process involves using a gas jet device to direct cooling gas at a high flow rate at a temperature of 25°C to the solidified material adjacent to the liquid-solid boundary of the molten metal. The deposition continues until the workpiece is complete. The workpiece is allowed to cool to a temperature below 400°C or lower within the deposition chamber. The workpiece is then removed from the deposition chamber, and the pre-bent substrate is then removed from the fixture. Depending on the operator's removal speed, the pre-bent substrate can be removed from the fixture at a temperature of 200-300°C or lower. In this case, the pre-bent substrate is removed from the fixture at a temperature of approximately 250°C.

[0234] like Figure 13CAs shown, the workpiece exhibits a small (only about 0.5 mm) upward movement at the short edge of the substrate, which suggests that the use of a bending clamping die combined with pre-bending and preheating eliminates the large amount of residual stress observed in the test substrate when using a conventional DED process.

[0235] Under the same conditions described above, repeatability was tested using similar substrates and the same workpiece design. The method demonstrated consistent repeatability results across all three produced workpieces. The substrate deformation deviation between workpiece #1 and workpiece #2 was approximately 0.5 mm, while the deviation between workpiece #2 and workpiece #3 was approximately 0.1 mm.

[0236] Stress-relief heat treatment has no significant effect on the overall dimensions of the workpiece. For example, after stress relief, only a small upward movement of about 0.5 mm occurs at the shorter edges of the plate. This means that due to the stress reduction, the residual stress in the workpiece in the deposited state is very low.

[0237] It will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its spirit or scope. Therefore, this invention is intended to cover such modifications and variations, provided they fall within the scope of the appended claims and their equivalents.

[0238] List of reference numerals

[0239] Below is a list of reference numerals used in the specification and accompanying drawings.

[0240] 100 Bending clamping mold 372 Third pre-bending heating path

[0241] 105 Knurled or corrugated surface 373 Fourth pre-bending heating path

[0242] 110 Top surface 374 Fifth pre-bending heating path

[0243] 115 Edge 375 Sixth Pre-bending Heating Path

[0244] 120 Ridge 380 Precast Wall

[0245] 130 Groove 382 Precast Wall

[0246] 140 Straight edge 384 Precast wall

[0247] 150 Ceramic Coating 400 Fixture

[0248] 155 Bonding coating 410 Nominal substrate deflection

[0249] 160 cavity 500 clamp

[0250] 162 cavity 501 threaded hole

[0251] 164 cavities, 502 holes

[0252] 166 cavity 505 bottom contact surface

[0253] 170 Reinforcing member 506 Side contact surface

[0254] 180 Maximum height 507 Top surface of the clamp

[0255] 200 Gas injection device 509 Ceramic coated surface

[0256] 210 Nozzle 510 Countersunk Screw

[0257] 230 Support component 515 Countersunk screw tip

[0258] 250 PTA welding torch, 520 bolts

[0259] 300 substrate 525 nut

[0260] 310 Top surface of the first side 530 fixture

[0261] 320 Second side 540 Alumina insulation board

[0262] 330 Prefabricated DED rear wall 541 Alumina insulation board

[0263] 350 Melting trajectory 542 Alumina insulation board

[0264] 355 Space between melting trajectories 543 Alumina insulation board

[0265] 360° melting trajectory; 544° region of uneven pressure and heat transfer distribution.

[0266] 370 First pre-bending heating path 545 Region with uneven pressure and heat transfer distribution

[0267] 371 Second pre-bending heating path

[0268] 546 Regions with uneven pressure and heat transfer distribution

[0269] 547 Regions with uneven pressure and heat transfer distribution

[0270] 548 Regions with uneven pressure and heat transfer distribution

[0271] 549 Regions with uneven pressure and heat transfer distribution

[0272] 550 base plate

[0273] 575 shows a box illustrating a region with non-uniform pressure and heat transfer distribution.

[0274] 576 shows a box illustrating a region with non-uniform pressure and heat transfer distribution.

[0275] 577 shows a box illustrating the region of non-uniform pressure and heat transfer distribution.

[0276] 578 shows a box illustrating a region with non-uniform pressure and heat transfer distribution.

[0277] 600 precast components

[0278] 600' precast component

[0279] 610 Clamping Entity

[0280] 615 Clamping Entity

[0281] 620 Clamping Entity

[0282] 625 Clamping Entity

[0283] 630 Clamping Entity

[0284] 650 Non-optimal clamping area

[0285] 700 First Preheating Heating Path

[0286] 705 Second Preheating Heating Path

[0287] 710 Third Preheating Heating Path

[0288] 715 Fourth Preheating Heating Path

[0289] 720 Fifth Preheating Heating Path

[0290] 725 Sixth Preheating Heating Path

[0291] 730 Seventh Preheating Heating Path

[0292] 735 Eighth Preheating Heating Path

Claims

1. A bending clamping die for mitigating distortion in a metal object manufactured using a directional energy deposition additive manufacturing process, wherein the bending clamping die is used as a support between a pre-bent substrate and a clamp in the manufacturing process, comprising: The first side, including Two or more cavities, separated by one or more reinforcing members; as well as The edge has a flat surface surrounding the periphery of the first side; The second side, opposite to the first side, has a curved surface and includes knurling or corrugation; as well as A ceramic coating is applied to the second side. The first side is the bottom surface of the mold. The first side may point toward the clamp, and the second side may be guided away from the clamp and toward the pre-bent substrate and positioned against the pre-bent substrate.

2. The bending clamping mold according to claim 1, wherein, The reinforcing member maintains the rigidity of the mold or provides resistance to mold deformation, or both.

3. The bending clamping mold according to claim 1 or 2 further comprises a non-magnetic metal.

4. The bending clamping die according to claim 1 or 2 further comprises a metal with a melting point of 1350°C or higher.

5. The bending clamping mold according to claim 3, wherein, The metal includes austenitic stainless steel.

6. The bending clamping mold according to claim 5, wherein, The austenitic stainless steel includes carbon, chromium, copper, manganese, molybdenum, nickel, nitrogen, phosphorus, silicon, or any combination of two or more of these.

7. The bending clamping mold according to claim 5, wherein, The austenitic stainless steel contains at least 18% chromium.

8. The bending clamping mold according to claim 5, wherein, The austenitic stainless steel is a 300 series stainless steel.

9. The bending clamping mold according to claim 5, wherein, The austenitic stainless steel includes 304 stainless steel, 309 stainless steel, 310 stainless steel, 316 stainless steel, 318 stainless steel, 321 stainless steel, or 330 stainless steel.

10. The bending clamping mold according to claim 1 or 2, wherein, The ceramic coating comprises zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, alkaline earth metal silicates, ZrV2O7, Mg3(VO4)2, or combinations thereof.

11. The bending clamping mold according to claim 1 or 2, wherein, The ceramic coating comprises ZrO2·8Y2O3.

12. The bending clamping mold according to claim 1 or 2, wherein, The ceramic coating has a thickness of 0.1 mm to 5 mm.

13. The bending clamping die according to claim 1 or 2, further comprising a nominal die deflection of 3 mm to 35 mm.

14. The bending clamping mold according to claim 1 or 2 further includes an adhesive coating, wherein the ceramic coating is applied to the adhesive coating.

15. A method for directional energy deposition in the production of metal workpieces, comprising: A pre-bent substrate is produced by using thermal energy to pre-bend the substrate by forming multiple melting tracks on the first surface of the substrate using a melting tool. The bending clamping mold according to any one of claims 1 to 14 is used as the lower support structure supporting the pre-bent substrate, and the pre-bent substrate and the bending clamping mold supporting the pre-bent substrate are fixed to the fixture using a plurality of clamps. as well as The metal workpiece is formed on a second surface of the substrate using an additive manufacturing process, the additive manufacturing process including melting a metal raw material to deposit a molten metal layer on the second surface of the substrate to form a base material, and depositing subsequent molten metal layers on the base material to form the workpiece. The second surface of the substrate is opposite to the first surface of the substrate.

16. The method according to claim 15, wherein, The metal raw material is a metal in the form of powder, wire, or a combination thereof.

17. The method of claim 15 or 16, further comprising preheating the pre-bent substrate to a temperature of 400°C to 900°C by applying thermal energy to the second side of the substrate before forming the metal workpiece while it is being secured to the fixture.

18. The method according to claim 15 or 16, wherein, Pre-bending the substrate involves inducing a thermal gradient within the substrate.

19. The method according to claim 15 or 16, wherein, The melting tool includes a heat source selected from laser beams, electron beams, plasma arcs, gas tungsten arcs, gas metal arcs, and any combination thereof.

20. The method according to claim 15 or 16, wherein, During the pre-bending of the first surface of the substrate, the area where heat energy is applied reaches a temperature that is the melting point of the metallic material, or a temperature that is 5°C to 50°C below or above the melting point of the metallic material.

21. The method according to claim 15 or 16, wherein, During the pre-bending of the first surface of the substrate, the formation of the melt tracks results in tensile stress at the center line of each melt track and compressive stress in regions away from the center line of each melt track as the substrate cools.

22. The method according to claim 21, wherein, The tensile stress at the center line of the melting trajectory is within 10% of the yield strength of the substrate.

23. The method according to claim 21, wherein, The tensile stress at the center line of the melting trajectory exceeds the yield strength of the substrate.

24. The method according to claim 15 or 16, wherein, The pre-bending step also includes using a gas jetting device to direct cooling gas toward the melting trajectory to accelerate the cooling of the melting trajectory.

25. The method according to claim 24, wherein, The cooling gas is directed toward the melting trajectory to form a thermal gradient in the substrate and to transmit residual stress in the substrate during cooling.

26. The method according to claim 24, wherein, The gas injection device directs the cooling gas toward the melting trajectory at a rate of 50 L / min to 500 L / min.

27. The method according to claim 24, wherein, The cooling gas is applied in a constant flow, or intermittently, or in a pulsed flow.

28. The method according to claim 24, wherein, The cooling gas includes an inert gas selected from argon, helium, neon, xenon, krypton, and combinations thereof.

29. The method according to claim 24, wherein, The cooling gas is applied at a temperature of 100°C or lower.

30. The method according to claim 24, wherein, The cooling gas is applied at a temperature of 25°C or lower.

31. The method according to claim 24, wherein, The gas injection device generates turbulence, laminar flow, or a combination of turbulence and laminar flow of the cooling gas.

32. The method according to claim 24, wherein, The melting tool includes a heat source selected from laser beams, electron beams, plasma arcs, gas tungsten arcs, gas metal arcs, and any combination thereof, and wherein the gas jetting device includes a plurality of nozzles that guide the cooling gas in a direction away from the heat source of the melting tool, and at least one nozzle guides the cooling gas to the solidified metal of the melting trajectory.

33. The method according to claim 15 or 16, wherein, The melting trajectories are generated at equal intervals.

34. The method according to claim 15 or 16, wherein, The distance between the melting trajectories is 10 mm to 60 mm.

35. The method according to claim 15 or 16, further comprising: Determine the centerline of each wall of the preform to be formed on the second surface of the substrate; as well as The melting trajectory on the first surface of the substrate is positioned 10 mm to 20 mm away from the centerline of most of the wall of the preform to be formed on the second surface of the substrate.

36. The method of claim 15 or 16, further comprising forming a majority melt line on the first surface at one or more locations other than those corresponding to one or more regions occupied by one or more walls of the workpiece to be formed on the second side of the substrate.

37. The method according to claim 15 or 16, wherein, The pre-bending forms a pre-bent substrate with uniform elastoplastic bending.

38. The method of claim 15 or 16, further comprising pre-bending the substrate while it is clamped to the fixture and thermally insulated from the fixture.

39. The method according to claim 15 or 16, wherein, One or more clips include an insulating coating on each surface that contacts the pre-bent substrate.

40. The method according to claim 39, wherein, The insulating coating includes ceramic materials, silicon carbide, silicon nitride, boron carbide, or combinations thereof.

41. The method according to claim 40, wherein, The ceramic material includes alumina, zirconium oxide, titanium oxide, alkaline earth metal silicates, aluminum titanate, zirconium dioxide, zirconium dioxide stabilized by the addition of yttrium oxide, yttrium aluminum oxide, ZrV2O7, Mg3(VO4)2, or combinations thereof.

42. The method according to claim 40 or 41, wherein, The thickness of the insulating coating is from 0.1 mm to 5 mm.

43. The method according to claim 39, wherein, The clip has a knurled pattern or corrugations on the surface that contacts the pre-bent substrate.

44. The method of claim 39, further comprising tightening the clamp to bring the pre-bent substrate into full contact with the lower bending clamping die.

45. The method according to claim 44, wherein, Tighten each clamp to a torque of 10 N·m to 100 N·m.

46. ​​The method according to claim 39, wherein, The clamps are positioned such that they intersect at the beginning or end of the wall of the workpiece being produced.

47. The method according to claim 15 or 16, wherein, The preheating of the pre-bent substrate is performed using one or more melting tools, including a DED heat source, under the following conditions: a) Forming a melting trajectory but not melting the surface of the pre-bent substrate; or b) Forming a melting trajectory and melting the surface of the pre-bent substrate at the melting trajectory.

48. The method of claim 46, further comprising positioning the melting tool at a spaced-apart position, the spaced-apart position being larger than the spaced-apart position for forming the workpiece.

49. The method of claim 48, further comprising preheating the pre-bent substrate to form a workpiece prior to DED deposition, the pre-bent substrate comprising a first short edge and an opposing second short edge, and a first long edge and an opposing second long edge, the preheating comprising: a) Position the melting tool, including the DED heat source, at the first short edge and within 10 mm to 60 mm of the first long edge of the pre-bent substrate fixed to the fixture; b) Apply thermal energy from the DED heat source of the melting tool across the surface of the pre-bent substrate, starting from the first short edge and extending across the surface of the pre-bent substrate to the opposite second short edge, to form a first energy line applied to the surface of the pre-bent substrate; c) Reposition the DED heat source of the melting tool to the first short edge and shift it from the first energy application line toward the second long edge by a distance of 10 mm to 60 mm; and d) Repeat steps b) and c) until an energy application line is applied across the surface of the pre-bent substrate to a position 10 mm to 60 mm from the opposite second long edge.

50. The method of claim 48 or 49 further comprises preheating the pre-bent substrate to form a workpiece by applying heat energy to the front side of the substrate using a heating device prior to DED deposition.

51. The method according to claim 50, wherein, The heating device includes an infrared heater, an induction heater, a resistance heater, or a combination thereof.

52. The method according to claim 50, wherein, The heating device includes a heat source for an inner conductor in a conduit, a heating strip, a resistance heating strip, an infrared heater, a ceramic heater with a positive thermal coefficient, a thick-film ceramic heater, a resistance wire heater, a resistance strip heating device, an infrared heater, an induction heater, or a combination thereof.

53. The method according to claim 15 or 16, wherein, Preheating raises the temperature of the pre-bent substrate to between 350°C and 650°C.

54. The method according to claim 16, wherein, The formation of the metal workpiece includes: Provide metal raw materials in the form of wires; A single melting tool is used to heat and melt the wire, causing molten metal material to be deposited onto a region of the substrate to form a base material; The base material is moved relative to the melting tool in a predetermined pattern, causing a continuous deposit of molten metal material on the base material to solidify and form a three-dimensional object.

55. The method according to claim 16, wherein, The formation of the metal workpiece includes: a) Provide metal raw materials in the form of wires; b) Heating at least a portion of the surface of the substrate using a first melting tool to form a preheated region on the substrate; c) The wire is heated and melted using a second melting tool, causing molten metal material to be deposited onto the preheated area to form a base material; d) Move the base material in a predetermined pattern relative to the positions of the first melting tool and the second melting tool; e) Heating at least a portion of the surface of the base material using the first melting tool to form a preheated region on the base material, and depositing molten metal material generated by melting the metal material using the second melting tool onto the preheated region on the base material; and f) Repeat steps d) and e) to solidify the continuous deposit of molten metal material on the preheated area of ​​the base material and form a three-dimensional object.

56. The method of claim 54, further comprising: The cooling gas is guided through the surface of the molten metal material using a gas jet device, or impacted on the surface of the molten metal material, or impacted on the surface of the solidified material adjacent to the liquid-solid boundary of the molten metal material, or any combination thereof; and The base material is moved relative to the melting tool and the gas jet in a predetermined pattern, causing a continuous deposit of molten metal material to solidify and form the three-dimensional object.

57. The method of claim 55, further comprising: The cooling gas is guided through the surface of the molten metal material using a gas jet device, or impacted on the surface of the molten metal material, or impacted on the surface of the solidified material adjacent to the liquid-solid boundary of the molten metal material, or any combination thereof; and The base material is moved relative to the positions of the first melting tool, the second melting tool, and the gas jet in a predetermined pattern, so that a continuous deposit of molten metal material solidifies and forms the three-dimensional object.

58. The method according to claim 55, wherein: The first melting tool includes a plasma-transfer arc welding torch, a laser device, an electron beam device, or any combination thereof; and The second melting tool includes a plasma-transfer arc welding torch, a laser device, a coaxial powder feed nozzle laser system, an electron beam device, or any combination thereof.

59. The method according to claim 58, wherein: The first melting tool includes a first plasma-transfer arc welding torch, and the second melting tool includes a second plasma-transfer arc welding torch; or The first melting tool includes a laser device, and the second melting tool includes a PTA welding torch; or The first melting tool includes a plasma-transfer arc welding torch, and the second melting tool includes a laser device; or The first melting tool includes a laser device, and the second melting tool includes a coaxial powder feed nozzle laser system; or The first melting tool includes a plasma-transferred arc welding torch, and the second melting tool includes a welding torch coaxial powder feed nozzle laser system; or The first melting tool includes a plasma-transfer arc welding torch, and the second melting tool includes an electron beam device; or The first melting tool includes an electron beam device, and the second melting tool includes a PTA welding torch; or The first melting tool includes an electron beam device, and the second melting tool includes a laser device; or The first melting tool includes a laser device, and the second melting tool includes an electron beam device.

60. The method according to claim 59, wherein, When the second melting tool includes a plasma-transfer arc welding torch, the plasma-transfer arc welding torch of the second melting tool is electrically connected to a DC power supply, such that the electrode of the plasma-transfer arc welding torch of the second melting tool becomes a cathode, and the metal material becomes a consumable electrode that becomes an anode.

61. The method according to claim 15 or 16, wherein, Each of the pre-bending of the substrate, the preheating of the pre-bent substrate, and the forming of the metal workpiece is performed in a closed chamber containing an inert atmosphere.

62. The method according to claim 61, wherein, The inert atmosphere includes argon, neon, xenon, krypton, helium, or a combination thereof.

63. A system for directional energy deposition, comprising: A clamp for securing a pre-bent substrate; The bending clamping die according to any one of claims 1 to 14 is positioned between the clamps when the pre-bent substrate is fixed to the clamp; Clips for securing the pre-bent substrate to the fixture; One or more melting tools, including a DED heat source, for melting a metal source into a molten metal material, said molten metal material being deposited on the surface of a base material; A gas jetting device is used to guide cooling gas to impact the solidified material at the liquid-solid boundary adjacent to the molten pool in order to affect the temperature gradient. Cooling gas supply device; as well as An actuator for positioning and moving the base material relative to the melting tool and the gas jetting device.

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