In-situ control device and method for inhibiting metal additive manufacturing cracking

Abstract

The invention discloses an in-situ control device and method for inhibiting metal additive manufacturing cracking, and belongs to the technical field of metal additive manufacturing. According to the device, the two propelling structures are arranged on the two sides of the core base plate with the transverse gap, the two propelling structures make contact with the core base plate from the two sides of the core base plate correspondingly, so that in the additive manufacturing process, the two propelling structures assist in extruding shrinkage of the core base plate from the two sides of the core base plate; and it is ensured that the shrinkage speed of the core substrate can be matched with the shrinkage speed required by the formed part. The device disclosed by the invention is a device for regulating and controlling the local structure deformation of the substrate in situ, and the local deformation of the substrate is regulated and controlled in real time in the additive manufacturing process, so that the distribution and evolution of a stress field are regulated, the tensile stress is successfully converted into the pressure stress, and the generation and expansion of cracks are effectively inhibited.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and relates to an in-situ control device and method for suppressing cracking in metal additive manufacturing. Background Art

[0002] High-energy beam metal additive manufacturing (such as laser melting and electron beam melting) melts and deposits metal powder or wire point by point, path by path, and layer by layer through a strong heat source, providing an innovative approach for the design and manufacture of complex metal structures. This technology has broad application potential in aerospace, automotive industry, and medical devices, meeting the needs of complex shapes and high performance. However, the process is highly heterogeneous and rapid, involving multi-scale thermal, structural, and stress coupling, and temperature gradients of up to 10 6 K / m, cooling rate can be up to 10 6 K / s. The deposited metal undergoes multiple thermal cycles and is subject to strong mechanical constraints from the substrate and fixture, resulting in significant thermal stress, phase change stress, and mechanical constraint stress inside the finished product. These stresses are coupled and gradually accumulated, and if not controlled, may lead to cracking and failure.

[0003] In the additive manufacturing of difficult-to-weld alloys (such as nickel-based high-temperature alloy IN738), cracks often form at grain boundaries and continue to expand as the deposited layer grows. This phenomenon is particularly evident when the size and shape of the metal components are complex. The interactions of solidification, reheating cycles, and internal stresses in additive manufacturing become more complex, and the cracking problem becomes more prominent. At present, research on crack control in additive manufacturing of difficult-to-weld alloys mainly focuses on the following aspects: optimizing process parameters, developing new alloy materials, and applying preheating technologies. Although these methods provide ideas for controlling cracks, they still face challenges in implementation and may increase manufacturing costs or affect material properties.

[0004] The published patent CN 118321575 A discloses a smart substrate to prevent cracking of additively manufactured parts. The patent disassembles the substrate and opens a transverse gap in the core printing part of the substrate, which is not connected to the surface. In the printing process, once the substrate is heated, it can move in the horizontal direction, reducing the mechanical constraints of the substrate on the formed part and improving the deformation coordination of the heat-affected zone material during expansion and contraction. However, when printing large-sized parts and printing multiple layers during the printing process, the above technical solution is difficult to fully keep up with the deformation speed of the formed part due to the entire deformed substrate at the bottom, which limits the crack suppression effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an in-situ control device and method for suppressing cracking in metal additive manufacturing, so as to solve the problem that in the prior art, only gaps are opened on the substrate, and the shrinkage speed of the substrate is difficult to meet the deformation speed of the printed part.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: An in-situ control device for suppressing cracking in metal additive manufacturing comprises: a base, two suspensions are slidably connected to the base, a propulsion structure is respectively arranged at the opposite ends of the two suspensions, the two propulsion structures are arranged at the two ends of the core substrate in the longitudinal direction, respectively abutting against the two sides of the core substrate, and the two propulsion structures are coaxial with the core substrate; and a transverse gap is arranged on the core substrate.

[0007] A further improvement of the present invention is: Preferably, the two suspensions are arranged along the lateral direction of the base; The base is connected with the suspension through the guide rail, and both ends of each suspension are respectively connected with a guide rail in a sliding manner.

[0008] Preferably, a motor is provided on the base, and the motor is used to drive the two ends of the suspension to move relative to the guide rail.

[0009] Preferably, the guide rail is a lead screw structure, and both ends of the suspension are slider structures.

[0010] Preferably, an upper panel is provided on the base, the upper panel is fixed to the base via a bracket, and a slot for placing the guide rail is opened on the upper panel.

[0011] Preferably, a top plate is arranged below the suspension, the top plate and two ends of the base plate are butted against each other in the longitudinal direction, and the core base plate is arranged in the base plate.

[0012] Preferably, the propulsion structure is in the shape of a pin, a block or a cylinder.

[0013] Preferably, the propulsion structure is in the shape of a thimble.

[0014] An in-situ control method for suppressing cracking in metal additive manufacturing based on the above-mentioned in-situ control device, in which during the additive manufacturing molten deposition process, two propulsion structures propel a core substrate from both sides of the core substrate.

[0015] Preferably, the propulsion speed of the propulsion structure is determined according to the contraction speed of the core substrate.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses an in-situ control device for suppressing cracking in metal additive manufacturing. Based on the above research, the device sets two propulsion structures on both sides of the core substrate with transverse cracks. The two propulsion structures counteract the core substrate from both sides, so that during the process of additive manufacturing, the two propulsion structures promote the contraction of the core substrate from both sides, ensuring that the contraction speed of the core substrate can meet the contraction speed of the process parts in the process of additive manufacturing substrate. The device of the present invention is a device for in-situ regulating the deformation of the local structure of the substrate. During the manufacturing process, the local deformation of the substrate is regulated in real time, thereby adjusting the distribution of the stress field, converting the tensile stress into compressive stress, and effectively suppressing the generation and expansion of cracks. The core is to solve the uneven deformation of the material caused by repeated heating-cooling cycles during high-energy beam additive manufacturing, especially when the hot deposited layer is rapidly cooled and contracted, it is subject to strong mechanical constraints of the cold substrate, resulting in the high tensile stress accumulated layer by layer in the deposited layer becoming the main driving force for cracking. Through the dynamic deformation control of the device, the risk of cracking of parts can be fundamentally reduced. The invention also has the following advantages: (1) Strong compatibility: It is suitable for a variety of high-energy beam metal additive manufacturing processes such as laser, electron beam and arc, and has a wide range of applications.

[0017] (2) Reduce internal stress and prevent cracking: Effectively control internal stress during the additive manufacturing process of difficult-to-weld alloys to prevent cracking and failure of parts and ensure forming quality.

[0018] (3) Strong versatility and expanded process window: The device is suitable for a variety of substrate materials, has high adaptability to process parameters, has significant crack arrest effect, and is suitable for the promotion and application of additive manufacturing of difficult-to-weld metals.

[0019] The present invention also discloses an in-situ control method for suppressing cracking in metal additive manufacturing. In the process of additive manufacturing, the core substrate shrinks and propulsion force is applied to the core substrate from both sides to assist the shrinkage of the core substrate. The method proposes to control the stress field by in-situ controlling the deformation of the local structure of the substrate to achieve effective control of cracks. This method not only simplifies stress management in additive manufacturing, but is also expected to significantly improve the forming quality and reliability of difficult-to-weld alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the substrate.

[0021] Figure 2 It is a structural processing diagram for the substrate used; Figure 3 This is an IN738LC nickel-based high-temperature alloy part printed without using a deformation control device; Figure 4 Deformation control device designed for the purpose; Figure 5 For mounting the designed substrate on the deformation control device; Figure 6 for a 3D printing process using a deformation control device; Figure 7 This is a crack-free IN73 nickel-based high-temperature alloy part printed using a deformation control device.

[0022] Among them, 1. Motor; 2. Top plate; 3. Propulsion structure; 4. Suspension; 5. Base plate; 6. Guide rail; 7. Upper panel; 8. Base; 9. Core base plate. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0024] In the present invention, the longitudinal direction hereinafter refers to the length direction of the substrate 5 , which is the same as the length direction of the printed piece, and the transverse direction is perpendicular to the length direction of the substrate 5 .

[0025] The first aspect of the present invention discloses an in-situ control device for suppressing cracking in metal additive manufacturing, which includes a motor 1, a top plate 2, a propulsion structure 3, a suspension 4, a base plate 5, a guide rail 6, an upper panel 7 and a base 8. The base 8 is slidably connected with two suspensions 4, and each of the two suspensions 4 is provided with a propulsion structure 3 at the opposite ends. The two propulsion structures 3 are arranged at the two ends of the core base plate 9 in the longitudinal direction, respectively abutting against the two sides of the core base plate 9, and the two propulsion structures 3 are coaxial with the core base plate 9; a transverse gap is provided on the core base plate 9. The two suspensions 4 are arranged along the transverse direction of the base 8.

[0026] It should be noted that the present invention is a further study of the disclosed patent CN 118321575 A, and the disclosed core substrate 9 is the S3 portion in the disclosed patent CN 118321575 A. The core substrate 9 is a portion of the substrate 5, a portion cut from the substrate 5, and can move longitudinally relative to the substrate 5. The relevant parameters and contents of the core substrate 9 can be referred to the above disclosed patent.

[0027] The base 8 of the device is used as an integral supporting structure and is placed on the printer bed during printing to support the entire in-situ control device. An upper panel 7 is fixedly supported on the base 8 by a plurality of brackets, and the area of ​​the upper panel 7 is substantially equal to that of the base 8.

[0028] The support structure for placing the motor 1 and the guide rail 6 is provided between the base 8 and the upper panel 7. The upper panel 7 is provided with four notches along the guide rail 6. On the support structure, four guide rails 6 are provided, which are symmetrically arranged on both sides of the base plate 5 in pairs, and protrude from the notches respectively. The suspension 4 is a rod-shaped structure, which is horizontally arranged on the base 8. A slider structure is integrally provided at one end of each suspension 4, and the slider structure is slidably connected to a guide rail 6.

[0029] The two ends of the guide rail 6 and the suspension 4 are connected by a threaded screw, and the motor 1 drives the suspension 4 to move by rotating the screw.

[0030] Two motors 4 can be provided according to different output power ends, respectively provided on both sides of the base 8, or one motor can be provided.

[0031] Preferably, the slider structures on both sides of the suspension 4 are driven by a motor 4 so that the driving force is the same and uniform.

[0032] Two top plates 2 are also provided on the upper panel 7. Each top plate 2 is provided below the suspension 4. The inner end of each top plate 2 abuts against one end of the base plate. The two top plates 2 can stably fix the base plate body.

[0033] One end of the propulsion structure 3 is fixed on the suspension 4, and the other end is against one end of the core substrate 9. As the suspension 4 moves, the two propulsion structures 3 can jointly compress the core substrate 9. The axes of the two propulsion structures 3 and the axis of the core substrate 9 are the same, so that the core substrate 9 can be evenly stressed during the compression process.

[0034] It should be understood that the propulsion structure 3 can be in the shape of a pin, block, cylinder or other shapes, but the area of ​​the inner end of the propulsion structure 3 should be smaller than the area of ​​the two ends of the core substrate 9 to ensure that the inner end of the propulsion structure 3 can completely contact the end of the core substrate 9. It should be noted that the surface structure of the above-mentioned propulsion structure 3 can be adjusted according to the different areas of the ends of the core substrate 9, thereby giving the core substrate 9 sufficient propulsion force.

[0035] Preferably, the propulsion structure 3 is in the shape of a thimble, so that the propulsion structure has strong adaptability.

[0036] The present invention also discloses an in-situ control method for suppressing cracking in metal additive manufacturing, the method comprising the following steps: 1) Select the substrate: Mark the CAD bottom surface shape of the part to be printed as shape C0, design a slightly larger rectangular shape C1, completely cover C0 and make C1 slightly larger than C0. Select a block plate with a thickness of usually more than 12 mm as the substrate R, and its horizontal cross-sectional size is generally larger than shape C1 (about 3 to 10 times that of C1). Align the center of C1 with the center of the upper surface of the substrate, determine the printed deposition area C2, and make C2 equal to C1.

[0037] 2) Processing substrate structure: Take out the upper part of the substrate corresponding to the C2 area from the substrate R, which is recorded as R1. The specific steps include first making a zigzag cut along the vertical thickness direction of the long side of the C2 rectangle, and then making a horizontal cut along the plane parallel to the C2 plane, with a cutting depth of 3 to 7 mm, and the horizontal cutting distance is consistent with the width of C2. At this time, the substrate R is divided into the R1 part and the remaining substrate body R2, and R1 can only move on the horizontal plane but not in the vertical direction.

[0038] 3) Cutting slits: Cut a series of slits from bottom to top along the vertical direction of R1. These slits are parallel to the horizontal long side of R1 and are spaced 3 to 8 mm apart. Make sure that the upper surface of R1 is not completely cut off. The processed R1 is recorded as the core substrate R3. The designed substrate containing R2 and R3 is recorded as substrate DR.

[0039] 4) Build a deformation control device: Build a working platform with ejectors on both sides. The two ejectors can move toward or away from each other on the same track. The movement speed of the two is the same and is controlled by the rotation of the lead screw on the track. The movement speed is automatically controlled by the motor.

[0040] 5) Install the designed substrate on the deformation control device: Assemble the designed substrate R2 and the core substrate R3 and fix them on the deformation control device so that both ends of the core substrate R3 are in contact with the ejector pins and keep them coaxial.

[0041] Stress control in the 3D printing process: Set appropriate additive manufacturing process parameters, and print layer by layer in the C2 area of ​​the designed substrate. At the same time, use an in-situ deformation control device to gradually compress the substrate R3 along the length direction of the substrate to suppress stress accumulation and cracking of metal parts.

[0042] During the printing process, the advancing speed of the two advancing structures is usually determined by dividing the compression length and time of the core substrate 9 when no advancement is performed. Further, the speed can be adjusted in real time according to the printing situation.

[0043] Furthermore, the propulsion force of the propulsion structure during the printing process is determined according to the friction force exerted on the core substrate when the molded part cools and shrinks during the printing process. During the propulsion process, if the propulsion structure 3 receives resistance force from both sides of the core substrate, the propulsion force needs to be reduced in a timely manner to ensure that the speed of the propulsion structure 3 is stable and controllable.

[0044] The following is further described in conjunction with specific embodiments.

[0045] Example To facilitate practitioners in the field to deeply understand the present invention, the technical solution of the present invention is described in detail below in conjunction with the accompanying drawings. Now, taking laser direct energy deposition technology as a representative of high-energy beam additive manufacturing, and taking typical metal parts as an example, the present invention explains how to effectively suppress the cracking of parts in the metal additive manufacturing process by adopting an in-situ deformation control device. To demonstrate the technical effect of the present invention, IN738LC nickel-based high-temperature alloy, a typical crack-prone material, is taken as an example.

[0046] First, prepare two steel substrates, denoted as R, with dimensions of 200×28×20 mm³ (see Figure 1 ).according to Figure 2 After mechanical processing, two designed substrates are obtained, which are recorded as substrates DR. One of the DR substrates is directly used for 3D printing of IN738LC nickel-based high-temperature alloy parts, and the other DR substrate will be matched with an in-situ deformation control device for 3D printing of IN738LC nickel-based high-temperature alloy parts.

[0047] Both working conditions use laser coaxial powder feeding direct energy deposition technology. The process conditions are 10,000-watt fiber laser (wavelength 960-1200 nm), laser power 4500 W, scanning speed 15 mm / s, layer lift 0.35 mm, and spot diameter 5.0 mm.

[0048] Using a DR substrate to directly deposit IN738LC nickel-based high-temperature alloy, printed parts such as Figure 3 As shown, it can be seen that there is still a vertical crack in the center of the sample, passing through multiple layers of deposition, which is mainly caused by excessive internal stress accumulation during the printing process.

[0049] In order to control the cracking of parts during the additive manufacturing process of IN738, an in-situ deformation control device was designed, such as Figure 4 shown. Figure 5 The designed substrate is shown to be assembled into an in-situ deformation control device. Figure 6 During the 3D printing process, the in-situ deformation control device squeezes the R3 part of the DR substrate in real time, and the part is compressed along the scanning direction. Since the tensile stress is mainly along the scanning direction, the tensile stress in the deposited layer can be converted into compressive stress by compressing the R3 part of the DR substrate, thereby significantly reducing the risk of cracking.

[0050] By using the in-situ deformation control device, 200 layers of deposition were 3D printed, and finally a crack-free IN738 part with a size of 180×60×10 mm³ was successfully printed. Figure 7 shown.

[0051] The present invention discloses an in-situ control device and method for suppressing cracking in metal additive manufacturing. The device is provided with two propulsion structures on both sides of a core substrate that has been provided with a transverse gap. The two propulsion structures contact the core substrate from both sides of the core substrate, respectively, so that during the additive manufacturing process, the two propulsion structures assist in squeezing the contraction of the core substrate from both sides of the core substrate, ensuring that the contraction speed of the core substrate can match the contraction speed required by the formed part. The device of the present invention is a device for in-situ regulating the deformation of the local structure of the substrate. During the additive manufacturing process, the local deformation of the substrate is regulated in real time, thereby adjusting the distribution and evolution of the stress field, successfully converting the tensile stress into the compressive stress, and effectively suppressing the generation and expansion of cracks.

[0052] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In the description of the present invention, the first feature "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features not being in direct contact but being in contact through another feature between them.

[0053] In the description of the present invention, “on”, “over” and “above” a first feature from a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature.

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0056] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An in-situ control device for suppressing cracking in metal additive manufacturing, characterized in that: include: A base (8), wherein two suspensions (4) are slidably connected to the base (8), and a propulsion structure (3) is respectively provided at opposite ends of the two suspensions (4). The two propulsion structures (3) are arranged at two longitudinal ends of a core substrate (9) and respectively abut against two sides of the core substrate (9). The two propulsion structures (3) and the core substrate (9) are coaxial; and a transverse slit is provided on the core substrate (9).

2. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 1, characterized in that: The two suspensions (4) are arranged in a transverse direction of the base (8); The base (8) is connected to the suspension (4) via a guide rail (6), and both ends of each suspension (4) are slidably connected to a guide rail (6) respectively.

3. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 2, characterized in that: A motor (1) is provided on the base (8), and the motor (1) is used to drive the two ends of the suspension (4) to move relative to the guide rail (6).

4. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 2, characterized in that: The guide rail (6) is a lead screw structure, and both ends of the suspension (4) are slider structures.

5. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 2, characterized in that: An upper panel (7) is provided on the base (5), the upper panel (7) is fixed on the base (5) via a bracket, and a slot for placing the guide rail (6) is provided on the upper panel (7).

6. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 1, characterized in that: A top plate (2) is arranged below the suspension (4), the top plate (2) and two ends of the base plate abut against each other in the longitudinal direction, and the core base plate (9) is arranged in the base plate.

7. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 1, characterized in that: The propulsion structure (3) is in the shape of a pin, a block or a cylinder.

8. The in-situ control device for suppressing cracking in metal additive manufacturing according to claim 1, characterized in that: The propulsion structure (3) is in the shape of a thimble.

9. An in-situ control method for suppressing cracking in metal additive manufacturing based on the in-situ control device according to claim 1, characterized in that: In the additive manufacturing molten deposition process, two propulsion structures (3) propel the core substrate (9) from both sides of the core substrate (9).

10. The in-situ control method for suppressing cracking in metal additive manufacturing according to claim 9, characterized in that: The propulsion speed of the propulsion structure is determined according to the contraction speed of the core substrate (9).

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