Hydrothermal-assisted additive and subtractive manufacturing composite equipment and methods

Abstract

This application relates to a hydrothermal-assisted additive-subtractive manufacturing composite equipment and method. The composite equipment includes a forming cylinder, a lifting platform, an additive manufacturing device, and a subtractive manufacturing device. The forming cylinder is configured to hold hydrothermal fluid; the lifting platform carries and moves the workpiece; the additive manufacturing device performs directional energy deposition on the lifting platform to form the workpiece; and the subtractive manufacturing device performs subtractive processing on the additive workpiece. The formed portion of the workpiece is gradually immersed in the hydrothermal fluid by the lifting platform, and the subtractive manufacturing device performs in-situ subtractive processing on the workpiece while it is at a high temperature. This application utilizes the stable high-temperature field provided by the hydrothermal fluid to ensure that the workpiece remains in a uniform thermal state throughout the alternating additive and subtractive manufacturing process, avoiding the problems of residual stress accumulation, deformation, and uneven microstructure and properties caused by repeated heating and cooling cycles.

Description

Technical Field

[0001] This application relates to the field of additive and subtractive manufacturing technology, and in particular to an additive and subtractive composite equipment and method based on hydrothermal assistance. Background Technology

[0002] Additive manufacturing can form complex components, but the surface quality of the formed components is difficult to directly meet application requirements; subtractive manufacturing offers high precision, but it is difficult to process complex structures. Therefore, additive-subtractive composite manufacturing technology has emerged, which achieves a single processing cycle for complex and precision components by alternating material deposition and removal.

[0003] However, in existing additive-subtractive composite manufacturing processes, the workpiece repeatedly undergoes thermal cycles of heating and cooling, leading to the accumulation of residual stress and repeated thermal expansion and contraction of the material. This results in a decrease in the dimensional accuracy of the workpiece after subtraction, and may even cause deformation and cracking. In addition, re-deposition after interruption in the additive manufacturing process can easily lead to uneven microstructure and properties, seriously affecting the service performance and service life of the components. Summary of the Invention

[0004] To address the above problems, this application provides an additive-subtractive composite material equipment, comprising: A forming cylinder, the forming cylinder being configured to hold a hot liquid; A lifting platform is provided inside the forming cylinder and is used to support the workpiece and drive the workpiece to move up and down. An additive manufacturing apparatus configured to perform cladding deposition on a forming material on a lifting platform, such that the forming material is melted and deposited layer by layer to form the workpiece; A subtractive manufacturing apparatus, wherein the subtractive manufacturing apparatus is used to perform subtractive processing on the workpiece; In this process, the formed part of the workpiece is gradually immersed in the hot liquid by the lifting platform, and the subtractive manufacturing device performs in-situ subtractive processing on the workpiece while it is at a high temperature.

[0005] In one embodiment, the subtractive manufacturing apparatus and the additive manufacturing apparatus are integrated on the same multi-axis motion system, and the two can switch working positions, wherein: When additive manufacturing is performed, the additive manufacturing device moves to a working position above the lifting platform, and the subtractive manufacturing device moves out of the working area; When performing subtractive manufacturing, the subtractive manufacturing device moves to a working position above the lifting platform, while the additive manufacturing device moves out of the working area.

[0006] In one embodiment, the additive manufacturing apparatus includes a deposition head for additive manufacturing, and the subtractive manufacturing apparatus includes a subtractive manufacturing head for subtractive manufacturing. The deposition head and the subtractive manufacturing head are integrated at the end of the same robotic arm, and the end of the robotic arm is provided with an automatic switching mechanism for switching between the deposition head and the subtractive manufacturing tool.

[0007] In one embodiment, the subtractive manufacturing apparatus is mounted on a multi-axis motion system, and the additive manufacturing apparatus is mounted on another multi-axis motion system. The two apparatuses move independently to the working position above the lifting platform to switch positions.

[0008] In one embodiment, the subtractive manufacturing apparatus is located to the side of the lifting platform to process the side of the workpiece, while the additive manufacturing apparatus is located above the lifting platform to perform vertical deposition.

[0009] In one embodiment, the subtractive manufacturing apparatus includes at least one of a CNC milling spindle, a turning tool holder, a grinding tool, a laser cutting head, or an electrical discharge machining head.

[0010] In one embodiment, the subtractive manufacturing apparatus includes a cooling structure for reducing the thermal impact of a high-temperature environment on the subtractive manufacturing apparatus. The cooling structure includes any one of a water-cooled baffle, a ceramic heat shield, a copper reflector, or a tool cooling channel.

[0011] In one embodiment, the forming cylinder is equipped with a heating device and an electromagnetic induction coil. The heating device is used to heat and melt the hot liquid material into a hot liquid and maintain it at a predetermined temperature. The electromagnetic induction coil is arranged around the side wall of the forming cylinder and is used to heat and drive the hot liquid to flow when energized.

[0012] In one embodiment, during the subtractive manufacturing process, the subtractive area of ​​the workpiece is located above the surface of the hot liquid, and the subtracted portion of the workpiece is immersed in the hot liquid as the lifting platform descends after the subtractive process.

[0013] This application also provides an in-situ additive / subtractive manufacturing method, applied to the equipment mentioned in any of the above embodiments, including: The heat transfer medium is introduced into the forming cylinder and heated to the target working temperature. The substrate is fixed on the lifting platform so that it is immersed in the hot liquid, and at least the upper surface of the substrate is kept above the liquid surface. Under hydrothermal in-situ immersion conditions, directional energy deposition is performed on a substrate using an additive manufacturing device to deposit layers to form the shaped part of the workpiece. At the same time, the shaped part is gradually immersed into the hydrothermal liquid by a lifting platform. When the deposition height reaches the preset value, additive manufacturing is paused, and the deposited part under high temperature is processed in situ using a subtractive manufacturing device. After the material reduction is completed, the reduced part is immersed in the hot liquid and the above steps are repeated until the in-situ material addition and subtraction manufacturing of the entire workpiece is completed. The completed workpiece is immersed in a hot liquid for in-situ heat treatment. Turn off the heating device and allow the hot liquid to cool slowly to room temperature before removing the workpiece, or lift the workpiece out of the hot liquid and cool it to room temperature under inert gas protection.

[0014] In one embodiment, when performing in-situ subtractive processing on a deposited portion at a high temperature using a subtractive manufacturing apparatus, a thermal expansion allowance is reserved based on the material's coefficient of linear expansion, ensuring that the subtractive dimension is larger than the target dimension at room temperature; wherein... The formula for calculating the allowance for thermal expansion satisfies: in, ΔL This is the amount of thermal expansion. L 0 Target size for room temperature α This is the coefficient of linear expansion of the material. ΔT This is the difference between the subtractive processing temperature and room temperature.

[0015] In one embodiment, when the deposition portion under high temperature is processed in situ using a subtractive manufacturing apparatus, the preset value of the deposition height is greater than the sum of the molten pool depth and the hydrothermal wetting capacity.

[0016] The technical solutions provided by the embodiments of this application may include the following beneficial effects: As can be seen from the above embodiments, the additive-subtractive composite equipment of this application includes a forming cylinder, a lifting platform, an additive manufacturing device, and a subtractive manufacturing device. The forming cylinder is configured to hold a hydrothermal fluid; the lifting platform is located inside the forming cylinder and is used to support the workpiece and drive it to move up and down; the additive manufacturing device is used to perform directional energy deposition on the lifting platform to form the workpiece; the subtractive manufacturing device is used to perform subtractive processing on the workpiece. The formed part of the workpiece is gradually immersed in the hydrothermal fluid by the lifting platform, and the subtractive manufacturing device performs in-situ subtractive processing on the workpiece while it is at a high temperature. This application uses the stable high-temperature field provided by the hydrothermal fluid to ensure that the workpiece is always in a uniform thermal state during the alternating process of additive and subtractive processing, avoiding the problems of residual stress accumulation, deformation, and uneven microstructure caused by repeated heating and cooling cycles; at the same time, it uses the linear expansion coefficient of the material to accurately reserve shrinkage allowance during high-temperature subtractive processing, so that the workpiece accurately reaches the target size after cooling, which can effectively improve the dimensional accuracy and manufacturing consistency of complex components.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the description are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the additive and subtractive manufacturing equipment provided in one embodiment of this application from a single perspective.

[0020] Figure 2 This is a schematic diagram of the structure of another additive or subtractive manufacturing device provided in one embodiment of this application from a single perspective.

[0021] Figure 3 This is a schematic flowchart of an in-situ additive or subtractive manufacturing method provided in one embodiment of this application.

[0022] Figure label: 10. Forming cylinder; 20. Lifting platform; 201. Support plate; 30. Additive manufacturing device; 40. Subtractive manufacturing device; 100. Workpiece. Detailed Implementation

[0023] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. Various modifications, variations, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but can be changed as will become apparent upon understanding this disclosure, except for operations that must be performed in a particular order. Furthermore, descriptions of features known in the art may be omitted for clarity and brevity. The modes described in the following exemplary embodiments do not represent all modes consistent with this application. Rather, they are merely examples of apparatuses consistent with some aspects of this application as detailed in the appended claims.

[0024] As described in the background section, Directed Energy Deposition (DED) based on high-energy beams (such as lasers, electron beams, and electric arcs) is a typical additive manufacturing process with advantages such as high forming efficiency and small size limitations, and is widely used in the manufacturing of large and complex metal components. However, during the DED forming process, the deposited portion is exposed to the environment, and the temperature gradually decreases, forming a large temperature gradient, which leads to the accumulation of thermal stress and can easily cause workpiece deformation or even cracking.

[0025] To overcome the precision limitations of single additive manufacturing, existing technologies have developed additive-subtractive composite manufacturing schemes. This involves depositing several layers of additive material, pausing the deposition process, and then using subtractive machining to finish the currently formed portion, achieving better dimensional accuracy and surface quality. However, this alternating process has inherent drawbacks: during additive manufacturing, the workpiece is heated to a high temperature, and during subtractive manufacturing, it is usually necessary to wait for the workpiece to cool to room temperature or a lower temperature to ensure cutting accuracy and tool life, resulting in repeated heating-cooling thermal cycles. This cycle not only exacerbates residual stress but also leads to cumulative dimensional errors due to the irreversible thermal expansion and contraction of the material, making it difficult for the final workpiece to meet high-precision assembly requirements.

[0026] To address the issue of thermal stress, existing technologies have proposed hot-bath additive manufacturing, which involves immersing the formed part in high-temperature liquid metal. The workpiece temperature is controlled by the liquid medium, reducing the temperature gradient and alleviating thermal stress. However, these technologies only focus on the additive process and do not address its integration with subtractive manufacturing. In traditional additive-subtractive composite manufacturing, interruptions in additive manufacturing cause heat accumulation and dissipation. When additive manufacturing continues using the same process after subtraction, the microstructure and properties will differ from those manufactured without interruption, leading to a decrease in the overall repeatability of workpiece manufacturing.

[0027] Based on this, this application provides an additive-subtractive composite equipment, referring to... Figure 1 and Figure 2 It includes a forming cylinder 10, a lifting platform 20, an additive manufacturing device 30, and a subtractive manufacturing device 40.

[0028] Specifically, the forming cylinder 10 is configured to hold a hydrothermal fluid. The hydrothermal fluid can be elemental tin, gallium, indium, bismuth, lead, or alloys thereof, or a high-temperature salt nonmetallic material. The operating temperature of the hydrothermal fluid depends on the thermal sensitivity of the printing material; for example, the operating temperature of the hydrothermal fluid is 300°C-500°C.

[0029] A lifting platform 20 is located inside the forming cylinder 10 and is used to support the workpiece 100 and move the workpiece 100 up and down. The lifting platform 20 includes a support plate 201, which supports the workpiece 100 to be formed. The lifting platform 20 moves the support plate 201 up and down so that the workpiece 100 can be partially immersed or exposed in the hot liquid. Specifically, in the additive manufacturing process, the lifting platform 20 gradually immerses the formed part of the workpiece 100 into the hot liquid, while the thin layer to be deposited above the formed part remains above the liquid surface to receive the energy beam from the additive manufacturing apparatus 30.

[0030] The additive manufacturing apparatus 30 is configured to perform cladding deposition on a forming material on a lifting platform 20, so that the forming material is melted and deposited layer by layer to form a workpiece 100.

[0031] The subtractive manufacturing apparatus 40 is used to perform subtractive processing on the workpiece 100. After the additive deposition reaches a preset height, the additive process is paused, and the subtractive manufacturing apparatus 40 performs in-situ subtractive processing on the deposited portion of the workpiece 100, which is under high temperature. This application avoids the accumulation of residual stress and dimensional accuracy errors caused by repeated heating and cooling cycles in traditional processes by keeping the workpiece 100 in a stable high-temperature field provided by the hydrothermal fluid for alternating additive and subtractive processing. At the same time, since the overall temperature of the workpiece 100 is uniform and stable, shrinkage allowance can be accurately reserved according to the thermal expansion coefficient of the material during subtractive processing, so that the workpiece 100 can accurately reach the target size after cooling to room temperature.

[0032] In some implementations, reference continues. Figure 2 The lifting platform 20 also includes a forming substrate 202 located on the support plate 201. The forming substrate 202 is used to support the workpiece to be formed. The forming substrate 202 is detachably connected to the support plate 201. Before additive manufacturing begins, the forming substrate 202 is mounted on the support plate 201, and the forming substrate 202 is adjusted to a predetermined height by a lifting mechanism so that its upper surface is exposed above the hydrothermal liquid surface to receive the energy beam from the additive manufacturing apparatus. During additive manufacturing, the workpiece is deposited layer by layer on the forming substrate 202; after additive manufacturing is completed, the forming substrate 202 together with the workpiece on it can be removed from the support plate 201 without having to remove the workpiece separately from the substrate.

[0033] Specifically, the forming substrate 202 is made of the same or similar material as the workpiece to be formed, in order to reduce interfacial stress and deformation caused by differences in thermal expansion coefficients. For workpieces made of different materials, the forming substrate 202 of the corresponding material can be replaced.

[0034] Furthermore, the lower surface of the forming substrate 202 is in close contact with the upper surface of the support plate 201 to ensure that heat can be efficiently conducted from the hot liquid to the forming substrate and the bottom of the workpiece through the support plate, thus avoiding the workpiece bottom temperature being too low.

[0035] In some embodiments, during the subtractive manufacturing process, the subtractive area of ​​the workpiece 100 is always above the surface of the hot liquid, and after the subtractive process, the subtracted portion of the workpiece 100 is immersed in the hot liquid as the lifting platform 20 descends.

[0036] Specifically, the subtractive processing area is located above the liquid surface, which avoids interference from the hydrothermal fluid on the subtractive process, such as preventing direct contact between the cutting tool and the hydrothermal fluid, which could lead to thermal damage to the tool. This can be understood as immersing only the portion that has undergone subtractive processing and needs to maintain its temperature in the hydrothermal fluid, while the area being processed is exposed to an inert gas environment. This setup ensures both the convenience and precision of the subtractive operation, and allows the processed portion to be promptly kept warm or slowly cooled by the hydrothermal fluid, maintaining overall temperature uniformity.

[0037] In some embodiments, an oxide film is formed on the surface of the hydrothermal fluid in the forming tank 10. The oxide film can be configured as SnO2, such as a naturally formed tin oxide film when tin is used as the hydrothermal fluid. This configuration effectively isolates the hydrothermal pool from powder materials splashed during additive manufacturing and chips generated during subtractive manufacturing, thereby preventing contamination of the hydrothermal pool components, extending the service life of the hydrothermal fluid, and ensuring the stability of the hydrothermal thermophysical properties. Simultaneously, the oxide film also possesses a certain degree of self-healing capability, rapidly reforming after localized damage to maintain its insulating function.

[0038] In some implementations, refer to Figure 1 The subtractive manufacturing device 40 and the additive manufacturing device 30 are integrated on the same multi-axis motion system, and the two can switch working positions.

[0039] Specifically, during additive manufacturing, the additive manufacturing device 30 moves to a working position above the lifting platform 20, while the subtractive manufacturing device 40 moves out of the working area. The working position refers to the position where the deposition head of the additive manufacturing device 30 can be directly facing the surface of the workpiece 100 to be deposited, and where the energy beam can be precisely focused; the working area refers to the effective range of motion of the multi-axis motion system above the forming cylinder 10. Moving out of the working area means that the subtractive manufacturing device 40 moves to a safe position that does not affect the additive manufacturing operation.

[0040] Understandably, moving the subtractive manufacturing device 40 out of the working area can prevent it from being contaminated by splashes, heat radiation or dust during the additive manufacturing process, while also preventing it from blocking the energy beam or interfering with the motion of the additive manufacturing device 30.

[0041] Specifically, during subtractive manufacturing, the subtractive manufacturing device 40 moves to a working position above the lifting platform 20, while the additive manufacturing device 30 moves out of the working area. At this time, the subtractive head of the subtractive manufacturing device 40 is facing the area of ​​the workpiece 100 that needs to be subtracted, while the additive manufacturing device 30 moves to a safe position.

[0042] For example, the deposition head and the subtractive tooling head are integrated at the end of the same robotic arm, and the end of the robotic arm is provided with an automatic switching mechanism to realize the automatic switching between the deposition head and the subtractive tooling.

[0043] Specifically, the robotic arm is a six-axis or more degree-of-freedom articulated industrial robotic arm with a unified tool interface at its end. The deposition head and the subtractive processing head are each equipped with a tool holder that matches this tool interface.

[0044] Furthermore, the tool changing mechanism is also configured to automatically connect or disconnect the air, water, electrical, and signal lines required by each tool during switching. For example, it connects the protective gas and powder delivery lines to the deposition head, and the high-speed spindle power and coolant lines to the sublimation head. Further details will not be elaborated here.

[0045] This setup allows additive manufacturing and subtractive manufacturing to switch quickly at the same workstation and on the same robotic arm, without the need for additional independent gantry cranes or multiple robots. This significantly saves space in the forming chamber, reduces equipment costs, and improves the efficiency and positional accuracy of alternating additive and subtractive manufacturing operations.

[0046] In other embodiments, the subtractive manufacturing device 40 is mounted on a separate gantry or six-axis robotic arm, while the additive manufacturing device 30 is mounted on another motion mechanism. Both devices move independently to their respective working positions above the lifting platform 20 for switching. This approach is suitable for manufacturing large workpieces 100 and provides higher rigidity and load-bearing capacity.

[0047] In some other embodiments, reference is made to Figure 2 The subtractive manufacturing apparatus 40 is positioned to the side of the lifting platform 20 to perform subtractive machining on the workpiece 100 using side milling or grinding. The additive manufacturing apparatus 30 is positioned above the lifting platform 20 to perform vertical deposition. This approach is suitable for special workpieces 100 that require side machining, such as those that need to be milled or ground on the side.

[0048] It should be noted that the arrangement of the additive manufacturing apparatus 30 being located above the lifting platform 20 for vertical deposition and the subtractive manufacturing apparatus being located to the side is merely an illustrative example and does not constitute a limitation on the scope of protection of this application.

[0049] In other embodiments, the additive manufacturing apparatus 30 may also be positioned to the side of the lifting platform 20 for deposition at an angle. Examples include an angle of 30° to 60° to the vertical direction, to accommodate the forming requirements of workpieces with complex curved surfaces or special structural features, or to adjust the incident angle to avoid already formed features.

[0050] Furthermore, the specific spatial relationship between the additive manufacturing device 30 and the subtractive manufacturing device 40, as well as their respective processing angles, can be adaptively adjusted according to the geometric characteristics of the workpiece, the processing path planning, and the spatial constraints within the forming chamber. The additive manufacturing device 30 and the subtractive manufacturing device 40 are each independently mounted on a motion mechanism, and the switching between additive and subtractive workstations and the adjustment of the processing posture are achieved through the displacement of the motion mechanism. This application does not impose any limitations on this, as long as the additive manufacturing device and the subtractive manufacturing device can collaboratively complete the in-situ additive and subtractive processing of the workpiece in a hot bath environment.

[0051] Specifically, refer to Figure 2 In section a, the additive manufacturing apparatus 30 is positioned above the lifting platform 20 and is used to perform layer-by-layer deposition forming of the workpiece 100. The subtractive manufacturing apparatus 40 is positioned to the side of the forming cylinder 10, i.e., it is mounted on an independent motion mechanism in a lateral arrangement. After the additive manufacturing apparatus 30 completes the deposition of a preset number of layers, it moves out of the working area (e.g., retreats to a non-working position to the side of the forming cylinder), and the subtractive manufacturing apparatus 40 then moves from the side to the vicinity of the workpiece to perform subtractive machining such as lateral milling or grinding. This lateral arrangement is particularly suitable for scenarios requiring machining of the sides of the workpiece, such as machining the sidewalls of impeller blades or the lateral flow channels of a mold.

[0052] Understandably, the subtractive manufacturing device 40 is located to the side, effectively utilizing the vertical space above the forming cylinder 10 for the additive manufacturing device, without interference between the two. When a process switch is required, the additive manufacturing device 30 simply needs to be moved out of the working area, and the subtractive manufacturing device 40 can be moved in from the side. This arrangement simplifies the equipment structure, reduces costs, and ensures the independence and reliability of the additive and subtractive manufacturing processes.

[0053] In some embodiments, the subtractive manufacturing apparatus 40 includes at least one of a CNC milling spindle, a turning tool holder, a grinding tool, a laser cutting head, or an electrical discharge machining head. This application does not limit the specific type of the subtractive manufacturing apparatus 40, as long as it is capable of performing in-situ subtractive processing on the workpiece 100 in a hot bath environment.

[0054] Specifically, the laser cutting head can use pulsed laser or continuous laser. When using a pulsed laser, the laser is output in the form of intermittent short pulses, which is a cold processing method. Pulsed laser cutting can effectively ensure cutting accuracy, reduce the width of the heat-affected zone, control heat input, and avoid adverse effects on the structure and properties of the already formed parts of the workpiece. It is especially suitable for processing thin-walled structures, fine features, and heat-sensitive materials.

[0055] It should be noted that the above description of the selection of pulsed lasers and continuous lasers is only an illustrative example. This application does not impose strict restrictions on the specific type of laser cutting head, as long as it can achieve low heat input and high precision in-situ subtractive processing in a hot bath environment.

[0056] In some embodiments, the subtractive manufacturing apparatus 40 includes a cooling structure for reducing the thermal impact of a high-temperature environment on the subtractive manufacturing apparatus 40. The cooling structure includes any one of a water-cooled baffle, a ceramic heat shield, a copper reflector, or a tool cooling channel.

[0057] It is understood that the aforementioned cooling structures can be used individually or in combination, depending on the temperature gradient of the hot pool environment, the layout space of the subtractive manufacturing apparatus, and the needs of the processing conditions. For example, a ceramic heat shield and a water-cooled baffle can be installed simultaneously near the surface of the hot liquid, and an internal cooling channel can be provided at the cutting tool. This application does not limit the specific form and combination of the cooling structure, as long as it can effectively reduce the thermal impact of the high-temperature environment on the subtractive manufacturing apparatus 40. This arrangement enables the subtractive manufacturing apparatus 40 to operate stably for a long time in a hot pool environment of 300℃-500℃, avoiding processing errors caused by thermal deformation and ensuring the dimensional accuracy of in-situ subtractive manufacturing.

[0058] In some embodiments, the forming cylinder 10 is equipped with a heating device and an electromagnetic induction coil. The heating device is used to heat and melt the hot liquid material into a hot liquid and maintain it at a predetermined temperature; the electromagnetic induction coil is arranged around the side wall of the forming cylinder 10 and is used to heat and drive the hot liquid flow when energized.

[0059] Specifically, the heating device includes resistance heating rods, heating plates, or heating jackets, which are disposed inside the side wall or on the outer surface of the forming cylinder 10. The heating device first heats the solid hydrothermal material above its melting point to completely melt it, and continues to operate during the additive and subtractive processes, maintaining the hydrothermal fluid within a preset operating temperature range. The heating device can employ zone control, that is, independent heating units are set in different height areas of the forming cylinder 10 to dynamically adjust the heating power of each area according to the change in the immersion depth of the workpiece 100, ensuring the uniformity of the hydrothermal temperature field.

[0060] Furthermore, multiple sets of electromagnetic induction coils can be arranged along the height of the side wall of the forming cylinder 10, with appropriate spacing between each set. The heating device and electromagnetic induction coils can be alternately arranged from the bottom to the top of the forming cylinder 10 to fully utilize space while achieving uniform heating. The number of turns of the electromagnetic induction coils, the coil spacing, and the frequency and intensity of the current flowing through them can be adjusted according to the characteristics of the hot liquid.

[0061] This setup helps create a uniformly heated and controllable liquid medium environment within the hot tub. Compared to static hydrothermal fluid relying solely on heat conduction, the forced convection driven by the electromagnetic induction coil significantly improves the heat transfer coefficient between the hydrothermal fluid and the workpiece 100, keeping temperature differences across the formed portion of the workpiece 100 within a minimal range, thereby minimizing thermal stress. Simultaneously, the uniform temperature field provides reliable conditions for subsequent calculations of material reduction allowance based on the coefficient of linear expansion, avoiding discrepancies between actual shrinkage and theoretical calculations caused by localized temperature differences within the workpiece 100.

[0062] This application also provides a method for manufacturing an additive-subtractive composite equipment, applicable to the additive-subtractive composite equipment mentioned in any of the above embodiments. (Refer to...) Figure 3 The method includes steps S100 to S600.

[0063] Step S100: The heat medium material is introduced into the forming cylinder 10 and heated to the target working temperature. The substrate is fixed on the lifting platform 20 so that the substrate is immersed in the hot liquid, and at least the upper surface of the substrate is kept above the liquid surface.

[0064] Specifically, the hydrothermal material is selected based on the thermophysical properties of the workpiece 100 material and the chemical compatibility between the hydrothermal material and the workpiece 100. For example, for titanium alloys, stainless steel, or nickel-based high-temperature alloys, tin or tin-based alloys can be used as the hydrothermal material, with a melting point between 200℃ and 300℃, and the working temperature controlled between 300℃ and 500℃. The thermal medium material is introduced into the forming cylinder 10 and heated to the target working temperature. At the same time, the electromagnetic induction coil is activated to ensure that the hydrothermal temperature is uniformly and stably maintained at the preset working temperature.

[0065] Furthermore, the printing substrate is fixed on the lifting platform 20, and the height of the lifting platform 20 is controlled so that most of the substrate is immersed in the hot liquid, leaving only the upper surface of the substrate or a thin layer area slightly above the upper surface exposed above the liquid surface so as to receive the energy beam of the additive manufacturing apparatus 30.

[0066] Step S200: Under in-situ hydrothermal immersion conditions, directional energy deposition is performed on the substrate using the additive manufacturing apparatus 30 to deposit the formed part of the workpiece 100 layer by layer, while the formed part is gradually immersed into the hydrothermal liquid by the lifting platform 20.

[0067] Specifically, the additive manufacturing apparatus 30, such as a laser-guided energy deposition head, is activated to deposit material layer by layer onto the substrate according to a preset path. After each layer is deposited, the lifting platform 20 descends by one layer thickness, exemplarily by 0.01 mm to 4 mm, so that the deposited layer is gradually immersed in the hydrothermal fluid, while the new deposited layer remains above the fluid surface. Since the formed portion of the workpiece 100 is constantly immersed in the high-temperature hydrothermal fluid, its temperature is maintained at a level substantially the same as that of the hydrothermal fluid, thereby significantly reducing the temperature gradient and thermal stress between the deposited layers.

[0068] Step S300: When the deposition height reaches the preset value, the additive manufacturing is paused, and the deposition part under high temperature is processed in situ using the subtractive manufacturing device 40. During the subtraction process, a thermal expansion margin is reserved according to the linear expansion coefficient of the material so that the size after subtraction is larger than the target size at room temperature.

[0069] Specifically, after depositing several layers, for example, when the deposition height reaches 5mm-20mm, the additive manufacturing device 30 is stopped and the subtractive manufacturing device 40 is moved to the working position.

[0070] Precision machining is performed on the outer contour, inner cavity, or flow channel of the deposited portion using CNC milling, turning, or grinding. Before subtractive machining, the linear expansion coefficient of the workpiece material is considered. α Processing temperature T (i.e., hydrothermal temperature, for example, 500°C) and room temperature T 0 (e.g., 20°C) difference ΔT and room temperature target size L 0 Calculate the allowable thermal expansion. ΔL =L 0 × α × ΔT .

[0071] In actual material reduction, the workpiece is machined to 100mm. L 0 + ΔL The dimensions. The amount of thermal expansion after workpiece 100 cools to room temperature. ΔL Disappeared, the workpiece size 100 shrunk exactly to L 0 In addition, an extra allowance for thermal deformation compensation and finishing, such as 0.05 mm, needs to be reserved according to the shape of the workpiece 100 to offset the effects of uneven shrinkage.

[0072] In some embodiments, taking commonly used additive manufacturing materials such as 316L stainless steel, Ti6Al4V titanium alloy, IN718 nickel-based superalloy, and AlSi10Mg aluminum alloy as examples, the average coefficient of linear expansion in the temperature range from 500°C to room temperature (20°C) is calculated.α The compensation rate is calculated as follows when preparing a workpiece with a target size of 100: The compensation rate in the table above is defined as the amount of thermal expansion. ΔL target size at room temperature L 0 The percentage, i.e., the compensation rate = ( α × ΔT The compensation rate is calculated as (1.056%) × 100%. As shown in the table, for the same material, the compensation rate is independent of the feature size and depends only on the material's coefficient of linear expansion and temperature difference. Different materials exhibit significantly different compensation rates due to differences in their coefficients of linear expansion. For example, the compensation rate of AlSi10Mg aluminum alloy (1.056%) is approximately 2.4 times that of Ti6Al4V titanium alloy (0.442%). Therefore, in high-temperature subtractive processing, the allowance must be accurately calculated based on the specific thermophysical properties of the material.

[0073] Specifically, taking the preparation of a 316L stainless steel sample with a target size of 100mm at room temperature as an example, when performing subtractive machining at a high temperature of 500℃, considering only the linear thermal expansion effect, the workpiece needs to be machined to 100.816mm. In addition, thermal deformation compensation must be reserved based on the specific geometry of the workpiece, and an additional finishing allowance (e.g., 0.05mm, to compensate for uncertainties such as tool wear and measurement errors) must be reserved. Through the comprehensive reservation of these three layers of allowances, a high-precision workpiece that accurately conforms to the target size after cooling to room temperature can be prepared in a one-time additive-subtractive composite manufacturing process. For a sample with a feature size of 50mm, similarly, a thermal expansion allowance of 0.408mm needs to be reserved, while the compensation rate remains unchanged.

[0074] It is understood that the temperature (500℃) and material in the above calculation example are only illustrative. In actual applications, the specific hydrothermal working temperature, workpiece material, and target dimensions should be considered according to the linear expansion formula Δ. L = L 0 × α × ΔT The corresponding calculations shall be performed. This application does not impose any restrictions on this.

[0075] Step S400: After the material reduction is completed, immerse the reduced part in the hot liquid and repeat steps S200 and S300 until the in-situ material addition and subtraction manufacturing of the entire workpiece is completed.

[0076] Specifically, after the subtractive processing is completed, the subtractive manufacturing apparatus 40 is moved out of the working area, and the lifting platform 20 is lowered so that the part of the workpiece that has just completed subtractive processing is completely immersed in the hot liquid. Then, step S200 is repeated for the next round of additive deposition, and then step S300 is repeated for the next round of subtractive processing. This process is repeated alternately until all feature layers of the workpiece have been deposited and subtracted, and finally a finished workpiece with accurate dimensions and a smooth surface is obtained.

[0077] Step S500: Immerse the completed workpiece entirely in the hot liquid for in-situ heat treatment.

[0078] Specifically, in-situ heat treatment includes: immersing the fully formed workpiece in a hydrothermal liquid, maintaining the hydrothermal liquid temperature above the phase transformation temperature or ductile-brittle transition temperature of the workpiece material, and holding it at that temperature for a preset duration (e.g., from 1 hour to 1000 hours, depending on the material and size).

[0079] For example, for Ti6Al4V titanium alloy, solution treatment and aging can be performed by holding at 700℃-800℃ for 2-6 hours; for IN718 nickel-based superalloy, stress-relief annealing can be performed by holding at 600℃-700℃ for 8-20 hours. In-situ heat treatment can further eliminate residual stress, stabilize the microstructure, and improve mechanical properties. After heat treatment, slow cooling is performed according to a preset cooling rate to avoid generating new thermal stress.

[0080] Step S600: Turn off the heating device, allow the hot liquid to cool slowly to room temperature, and then remove the workpiece, or lift the workpiece out of the hot liquid and cool it to room temperature under inert gas protection.

[0081] Specifically, when the melting point of the hydrothermal material is below room temperature, the heating device can be turned off directly, allowing the hydrothermal liquid to cool naturally to room temperature. If the hydrothermal liquid solidifies at this point, the workpiece will be encased in a solid and can be removed as a whole or separated after heating. When the melting point of the hydrothermal material is above room temperature, the heating device can be turned off first, allowing the hydrothermal liquid to cool slowly to slightly above its melting point. Then, the lifting platform 20 is raised to lift the workpiece above the hydrothermal liquid surface. Inert gas is introduced into the forming chamber for protection, allowing the workpiece to cool slowly to room temperature mainly through thermal radiation and limited heat conduction. Finally, the workpiece is removed, and any remaining hydrothermal liquid on the surface is cleaned.

[0082] This application achieves in-situ additive and subtractive composite manufacturing in a uniform and stable high-temperature field through the above method, effectively avoiding residual stress, deformation and uneven structure caused by repeated hot and cold cycles, and significantly improving the dimensional accuracy and service performance of complex metal components.

[0083] In some embodiments, when the subtractive manufacturing apparatus 40 performs in-situ subtractive processing on the deposited portion at high temperature, the preset value of the deposition height is greater than the sum of the molten pool depth and the hydrothermal wetting capacity.

[0084] Specifically, the melt pool depth refers to the maximum vertical depth of the liquid melt pool formed by the high-energy beam heat source during additive manufacturing; the hydrothermal wetting ability refers to the wettability between the hydrothermal fluid and the surface of the deposited material, characterized by the contact angle θ.

[0085] When the contact angle θ between the hydrothermal fluid and the material surface is less than 90°, it is defined as hydrophilic. The hydrothermal fluid is easy to spread along the material surface. At this time, the preset value of the deposition height needs to be greater than the sum of the molten pool depth and the hydrothermal fluid wetting height to avoid the hydrothermal fluid from entering the molten pool due to capillary action. When the contact angle θ between the hydrothermal fluid and the material surface is greater than 90°, it is defined as hydrophobic, and the hydrothermal fluid does not easily wet the material surface. In this case, the preset value of the deposition height can be greater than the depth of the molten pool, so as to reduce the requirement for deposition height and reduce the risk of hydrothermal contamination.

[0086] This application is particularly applicable to the manufacture and repair of complex metal components, such as large thin-walled structural parts, molds with internal cooling channels, integral impellers / disks, and remanufactured parts of high-value equipment.

[0087] By actively controlling the thermal boundary of the liquid metal hot pool and co-manufacturing with in-situ addition and subtraction of materials, this application can achieve coordinated control of the component's microstructure and geometric accuracy, meeting the high-precision and high-performance manufacturing requirements of complex metal components in the high-end manufacturing field.

[0088] In the above detailed description, reference has been made to the accompanying drawings, which illustrate specific aspects of how this disclosure can be practiced. In this regard, terms indicating direction or positional relationship, such as “thickness,” “upper,” “lower,” “top,” “bottom,” “inner,” and “outer,” can be used with reference to the orientation of the described figures. Since components of the described device can be positioned in several different orientations, these directional terms are for illustrative purposes and not for limitation. It should be understood that other aspects can be utilized and structural or logical changes can be made without departing from the concept of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0089] It should be understood that, unless otherwise specifically indicated, features of various embodiments of this disclosure described herein can be combined with each other. As used herein, the term “and / or” includes any one of the relevant listed items and any combination of any two or more; similarly, “at least one of…” includes any one of the relevant listed items and any combination of any two or more.

[0090] It should be understood that, unless otherwise expressly specified and limited, the terms "joining," "attaching," "installing," "connecting," "linking," "fixing," etc., used in the embodiments of this disclosure should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms herein based on the specific circumstances.

[0091] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, parts, regions, layers, or sections, these components, parts, regions, layers, or sections are not limited to these terms. Rather, these terms are used only to distinguish one component, part, region, layer, or section from another. Therefore, without departing from the teachings of the examples described herein, the first component, part, region, layer, or section mentioned in the examples may also be referred to as the second component, part, region, layer, or section. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include at least one of that feature. In the description herein, “a plurality” means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A hydrothermal-assisted additive-subtractive composite equipment, characterized in that, include: A forming cylinder, the forming cylinder being configured to hold a hot liquid; A lifting platform is provided inside the forming cylinder and is used to support the workpiece and drive the workpiece to move up and down. An additive manufacturing apparatus configured to perform cladding deposition on a forming material on a lifting platform, such that the forming material is melted and deposited layer by layer to form the workpiece; A subtractive manufacturing apparatus, wherein the subtractive manufacturing apparatus is used to perform subtractive processing on the workpiece; In this process, the formed part of the workpiece is gradually immersed in the hot liquid by the lifting platform, and the subtractive manufacturing device performs in-situ subtractive processing on the workpiece while it is at a high temperature.

2. The additive-subtractive composite equipment according to claim 1, characterized in that, The subtractive manufacturing apparatus and the additive manufacturing apparatus are integrated on the same multi-axis motion system, and the two can switch working positions, wherein: When additive manufacturing is performed, the additive manufacturing device moves to a working position above the lifting platform, and the subtractive manufacturing device moves out of the working area; When performing subtractive manufacturing, the subtractive manufacturing device moves to a working position above the lifting platform, while the additive manufacturing device moves out of the working area.

3. The additive-subtractive composite equipment according to claim 2, characterized in that, The additive manufacturing apparatus includes a deposition head for additive manufacturing, and the subtractive manufacturing apparatus includes a subtractive manufacturing head for subtractive manufacturing. The deposition head and the subtractive manufacturing head are integrated at the end of the same robotic arm, and the end of the robotic arm is provided with an automatic switching mechanism for switching between the deposition head and the subtractive manufacturing tool.

4. The additive-subtractive composite equipment according to claim 1, characterized in that, The subtractive manufacturing device is mounted on a multi-axis motion system, and the additive manufacturing device is mounted on another multi-axis motion system. The two devices move independently to the working position above the lifting platform to switch positions.

5. The additive-subtractive composite equipment according to claim 4, characterized in that, The subtractive manufacturing apparatus is located to the side of the lifting platform to process the side of the workpiece, while the additive manufacturing apparatus is located above the lifting platform to perform vertical deposition.

6. The additive-subtractive composite equipment according to claim 1, characterized in that, The subtractive manufacturing apparatus includes at least one of a CNC milling spindle, a turning tool holder, a grinding tool, a laser cutting head, or an electrical discharge machining head.

7. The additive-subtractive composite equipment according to claim 1, characterized in that, The subtractive manufacturing apparatus includes a cooling structure for reducing the thermal impact of high-temperature environments on the subtractive manufacturing apparatus. The cooling structure includes any one of a water-cooled baffle, a ceramic heat shield, a copper reflector, or a tool cooling channel.

8. The additive-subtractive composite equipment according to claim 1, characterized in that, The forming cylinder is equipped with a heating device and an electromagnetic induction coil. The heating device is used to heat and melt the hot liquid material into a hot liquid and maintain it at a predetermined temperature. The electromagnetic induction coil is arranged around the side wall of the forming cylinder and is used to heat and drive the hot liquid to flow when energized.

9. The additive-subtractive composite equipment according to claim 1, characterized in that, During the subtractive manufacturing process, the subtractive area of ​​the workpiece is located above the surface of the hot liquid, and the subtracted portion of the workpiece is immersed in the hot liquid as the lifting platform descends after the subtractive process.

10. A method for manufacturing an additive-subtractive composite equipment, characterized in that, The device used in any one of claims 1 to 9 comprises: The heat transfer medium is introduced into the forming cylinder and heated to the target working temperature. The substrate is fixed on the lifting platform so that it is immersed in the hot liquid, and at least the upper surface of the substrate is kept above the liquid surface. Under hydrothermal in-situ immersion conditions, directional energy deposition is performed on a substrate using an additive manufacturing device to deposit layers to form the shaped part of the workpiece. At the same time, the shaped part is gradually immersed into the hydrothermal liquid by a lifting platform. When the deposition height reaches the preset value, additive manufacturing is paused, and the deposited part under high temperature is processed in situ using a subtractive manufacturing device. After the material reduction is completed, the reduced part is immersed in the hot liquid and the above steps are repeated until the in-situ material addition and subtraction manufacturing of the entire workpiece is completed. The completed workpiece is immersed in a hot liquid for in-situ heat treatment. Turn off the heating device and allow the hot liquid to cool slowly to room temperature before removing the workpiece, or lift the workpiece out of the hot liquid and cool it to room temperature under inert gas protection.

11. The manufacturing method according to claim 10, characterized in that, When performing in-situ subtractive processing on a deposited portion at high temperature using a subtractive manufacturing apparatus, a thermal expansion allowance is reserved based on the material's coefficient of linear expansion, ensuring that the post-subtractive dimension is larger than the target dimension at room temperature; among which, The formula for calculating the allowance for thermal expansion satisfies: ； Where ΔL is the amount of thermal expansion, L0 is the target size at room temperature, α is the coefficient of linear expansion of the material, and ΔT is the difference between the subtractive processing temperature and room temperature.

12. The manufacturing method according to claim 11, characterized in that, When using a subtractive manufacturing device to perform in-situ subtractive processing on a deposited portion under high temperature conditions, the preset value of the deposition height is greater than the sum of the molten pool depth and the hydrothermal wetting capacity.

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