Additive manufacturing method of part

Abstract

The invention discloses an additive manufacturing method of a part, relates to the technical field of additive manufacturing, and aims to solve the problems that an existing complex part printing method cannot guarantee the deformation amount of a thin-wall inner cavity structure and buckling deformation is likely to occur. The method includes the steps that analog simulation is conducted on the additive manufacturing process of a target part, and a stress concentration area of the target part is determined; adding an auxiliary support in the stress set area to obtain a first target part; adjusting the first target part by adopting an anti-compensation method to obtain a second target part; removing the auxiliary support in the second target part to obtain a target three-dimensional model of the target part; performing region division and parameter setting on the target three-dimensional model according to a preset rule to obtain a printing file with uniformly changed energy density; and printing to obtain a target part. The additive manufacturing method of the part is used for reducing the deformation amount of the thin-wall inner cavity structure in the printing process, meanwhile, the problem of buckling deformation of a suspension structure is avoided, and the printing precision of the complex part is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to an additive manufacturing method for a part. Background Art

[0002] Many key structures use a large number of complex cavity thin-wall parts and protruding surface structures. The manufacturing cycle is long when using traditional technology to process them, which seriously hinders the task of model development. What's worse, many new complex parts cannot be processed using traditional processes at all.

[0003] Selective laser melting (SLM) is a widely used and mature process. This method is based on the basic idea of ​​rapid prototyping and adopts a layer-by-layer cladding additive manufacturing method. According to the three-dimensional model of the part, the model is sliced ​​and layered according to a certain thickness. Then, under the control of the CNC system, the laser is used to control the molten metal powder through the galvanometer to directly form parts with specific geometric shapes. Selective laser melting technology can realize moldless and rapid response manufacturing of complex cavities, space lattices and other special-shaped structures, which can greatly reduce the manufacturing process and shorten the production cycle. It has obvious advantages in the forming of complex metal parts, and can realize the integrated design and manufacturing of materials, structures and functions, providing an advanced technology for rapid verification of rapid response and precise manufacturing.

[0004] Selective laser melting of complex structural parts is an important component of many 3D printed parts. However, for complex parts with thin-walled inner cavity structures and emergent surface structures, large-scale thin-walled inner cavity structures are very prone to deformation during the selective laser melting process. Conventional control methods have a large amount of support, and the support removal process is prone to secondary deformation, affecting the printing accuracy of the parts. Moreover, during the selective laser melting process, the rapid melting and solidification of the material will produce a large temperature gradient, thereby inducing residual stress. Due to the lack of sufficient support, the overhanging structure is prone to warping and deformation under the action of residual stress, further affecting the printing accuracy of the parts. Summary of the invention

[0005] The purpose of the present invention is to provide an additive manufacturing method for parts, which is used to reduce the deformation of thin-walled inner cavity structures during printing, while avoiding the problem of warping and deformation of overhanging structures, and improving the printing accuracy of complex parts.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for additive manufacturing of a part, comprising:

[0008] Simulating the additive manufacturing process of the target part to determine the stress concentration area of ​​the target part; the stress concentration area at least includes a first stress concentration area, and the first stress concentration area is a stress concentration area at a thin-walled inner cavity structure;

[0009] Add auxiliary support in the first stress concentration area to obtain a first target part;

[0010] The first target part is adjusted by using a counter-compensation method to obtain a second target part;

[0011] removing the auxiliary support in the second target part to obtain a target three-dimensional model of the target part;

[0012] The target three-dimensional model is divided into regions and parameters are set according to preset rules to obtain a printing file; the energy density of the emergent surface structure of the target part in the printing file changes uniformly;

[0013] The target part is printed based on the print file to obtain the target part. The effect description of the first set of rights should be analyzed in detail. The writing method is:

[0014] Compared with the prior art, the additive manufacturing method of a part provided by the present invention determines the stress concentration area of ​​the target part by simulating the additive manufacturing process of the target part; then, auxiliary supports are added in the first stress concentration area, and the structural parameters of the method for counter-compensating the part with the auxiliary supports are adjusted. The counter-compensation method can make the obtained thin-walled inner cavity structure of the part still printable after removing the auxiliary supports, effectively improve the stability of the forming process, and can control the deformation of the thin-walled inner cavity structure within the required range. Through this method, it can be achieved that parts with thin-walled inner cavity structures can be printed without adding supports, and the deformation of parts can be greatly reduced without increasing the printing cost. It avoids the problem that the thin-walled inner cavity structure needs to add supports before it can be printed, and the support cannot be removed for some closed structures, which affects the accuracy of the parts or the removal of the supports causes secondary deformation of the thin-walled inner cavity structure. In addition, the target 3D model is divided into regions and parameters are set according to preset rules to obtain a printing file; the energy density of the emergent surface structure in the printing file changes evenly, avoiding the situation in which a large temperature gradient is generated by rapid melting and solidification of the material during laser selective melting, reducing the generation of residual stress, and thus avoiding the problem of warping and deformation of the emergent surface structure under the action of residual stress. This further improves the printing accuracy and forming quality of parts.

[0015] Optionally, the step of dividing the target three-dimensional model into regions and setting parameters according to preset rules to obtain a print file includes:

[0016] Slicing the target three-dimensional model according to a first preset thickness to obtain a plurality of slice layers;

[0017] Taking the emergent surface as the lower surface, a plurality of slice layers are segmented through a preset number of slice layers along a forming direction to obtain a target area; the target area includes a first area and a second area; the first area is the area where the emergent surface is located, and the second area is the area of ​​the target area other than the first area; the layer thickness of the first area is the first preset thickness; the layer thickness of the second area is greater than or equal to the first preset thickness; the emergent surface is the lower surface of the emergent surface structure;

[0018] The first region is divided according to a preset region width along a direction perpendicular to the forming direction to obtain a plurality of first sub-regions, and the second region is divided according to the preset region width along a direction perpendicular to the forming direction to obtain a plurality of second sub-regions;

[0019] Parameters are set for the first sub-region and the second sub-region to obtain a first parameter scheme; in the first parameter scheme, the energy density of the second region is greater than or equal to the energy density of the first region, the energy density of the first sub-region gradually decreases along a target direction, and the energy density of the second sub-region gradually decreases along the target direction; the target direction is a direction perpendicular to a forming direction and close to an edge of a part;

[0020] Parameters are set for the area in the slice layer except the target area to obtain a second parameter scheme; the first parameter scheme and the second parameter scheme constitute the printing file.

[0021] Optionally, the first region is divided according to a preset region width along a direction perpendicular to the forming direction to obtain a plurality of first sub-regions, and the second region is divided according to the preset region width along a direction perpendicular to the forming direction to obtain a plurality of second sub-regions, and the method further comprises:

[0022] The first sub-region and the second sub-region are layered according to the second preset thickness along the forming direction to obtain a first sub-region layering scheme and a second sub-region layering scheme; the first sub-region layering scheme is that the second preset thickness corresponding to the first sub-region gradually decreases along the target direction; the second sub-region layering scheme is that the second preset thickness corresponding to the second sub-region gradually decreases along the target direction;

[0023] The target part is printed according to the first sub-region layering scheme and the second sub-region layering scheme to obtain the target part.

[0024] Optionally, setting parameters for the first sub-region and the second sub-region to obtain a first parameter scheme includes:

[0025] The parameters of the first sub-area and the second sub-area are set according to the rule that the laser power is from large to small, the scanning speed is from slow to fast, and the line spacing is from small to large along the target direction to obtain a first parameter scheme.

[0026] Optionally, the number of the emergent surface structures is greater than 1 and the lower surfaces of different emergent surface structures are located in different slice layers; and the energy density of the first region in the same slice layer in the first parameter scheme is less than or equal to the energy density of the second region.

[0027] Optionally, the energy density of two adjacent first sub-regions is equal, and the energy density of two adjacent second sub-regions is equal.

[0028] Optionally, the adopting the anti-compensation method to adjust the first target part to obtain the second target part comprises:

[0029] With the auxiliary support as a supporting point, the shape of the first stress concentration area in the first target part is adjusted to change the deformation direction of the first stress concentration area until the first stress concentration area can be printed and formed when the auxiliary support is removed, thereby obtaining a second target part.

[0030] Optionally, the target part further includes an outer wall structure, the stress concentration area further includes a second stress concentration area, and the second stress concentration area is a stress concentration area at the outer wall structure; after adding auxiliary support to the first stress concentration area, the method further includes:

[0031] In the target part after adding the auxiliary support, determining a target outer wall structure in the second stress concentration region whose wall thickness is less than a preset wall thickness threshold and whose height is greater than a preset height threshold;

[0032] A mesh support structure is added to the outer surface of the target outer wall structure to obtain a first target part; the mesh support structure is composed of a plurality of mutually interwoven oblique ribs, and the meshes of the mesh support structure are in a diamond shape.

[0033] Optionally, before the first target part is adjusted by the anti-compensation method to obtain the second target part, the method further includes:

[0034] Importing the structure of the first target part except the auxiliary support into the anti-compensation software as a whole, and identifying the separation area of ​​the target part and the auxiliary support in the anti-compensation software;

[0035] Introducing the auxiliary support in the first target part into the separation area to complete the introduction of the first target part;

[0036] The first target part is adjusted by using a counter-compensation method to obtain a second target part.

[0037] Optionally, a surface of the auxiliary support close to the bottom of the target part is an inclined surface, an angle between a contact surface of the auxiliary support and the inclined surface is less than 40 degrees, and the contact surface is a surface in contact with the thin-wall inner cavity structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0039] Figure 1 A flow chart of an additive manufacturing method for a part provided by the present invention;

[0040] Figure 2 A top view of the thin-wall inner cavity structure after adding auxiliary support provided by the present invention;

[0041] Figure 3 A longitudinal cross-sectional view of the thin-wall inner cavity structure after adding auxiliary support provided by the present invention;

[0042] Figure 4 A schematic diagram of a self-forming auxiliary support structure provided by the present invention;

[0043] Figure 5 A schematic diagram of a partial outer wall structure with a mesh support provided by the present invention;

[0044] Figure 6 A schematic diagram of a part with a emergent surface provided by the present invention;

[0045] Figure 7 A schematic diagram of a target area division method provided by the present invention;

[0046] Figure 8 A schematic diagram of sub-area division provided by the present invention;

[0047] Fig. 9 A schematic diagram of the sub-region layering provided by the present invention;

[0048] Fig.10 A schematic diagram of layered area numbering provided by the present invention.

[0049] Reference numerals:

[0050] 1-thin-wall inner cavity structure, 2-auxiliary support, 3-net support structure, 4-emergent surface, 5-dividing line. DETAILED DESCRIPTION

[0051] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0052] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0053] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0054] With the development of science and technology, the structure of parts is becoming more and more complex. For complex parts with thin-walled inner cavity structures and emergent surface structures, complex thin-walled structures are prone to deformation during the forming process. As the requirements for the deformation of the part contour become smaller and smaller, the forming of complex thin-walled structures becomes more and more difficult. Conventional control methods have a large amount of control support, which is easy to cause secondary deformation of thin-walled structures during the removal process; and for parts with inner cavity structures, the internal deformation is large, which makes it impossible to compensate for the deformation of the outer wall. In the layer-by-layer accumulation and layered manufacturing process, the lower surface area of ​​the emergent surface structure of the part is in direct contact with the powder. Due to the hot forming characteristics of SLM layer-by-layer melting accumulation, the lower surface is prone to problems such as powder sticking and slag, and warping and deformation of the overhanging area during the manufacturing process. The forming quality of the part is directly related to the energy density. If the energy density is too high, the powder will be over-melted, causing excess liquid metal to splash and adhere to the overhanging surface. If the energy is too low, the powder cannot be fully melted, and the unmelted powder will directly adhere to the surface to form slag. If the scanning speed is too fast, the laser and powder interaction time is short, the powder is not completely melted, and the line spacing or layer thickness setting is unreasonable, the molten pool will solidify inconsistently, which may cause powder sticking and slag. In the laser melting process, the rapid melting and solidification of the material will produce a large temperature gradient, which will induce residual stress. Due to the lack of sufficient support, the overhanging structure will warp and deform under the action of residual stress. These problems seriously affect the printing accuracy and forming quality of the parts.

[0055] To solve these problems, the present invention provides an additive manufacturing method for parts. On the basis of the existing laser selective melting forming support addition, the large thin-walled inner cavity structure is analyzed and simulated, and auxiliary support is added for anti-compensation, which effectively improves the stability of the forming process, improves the forming quality of the parts, and reduces the occurrence of slag and warping. The following is an explanation with reference to the accompanying drawings.

[0056] Figure 1 A flowchart of an additive manufacturing method for a part provided by the present invention, such as Figure 1 As shown, the method comprises the following steps:

[0057] Step S1: simulating the additive manufacturing process of the target part to determine the stress concentration area of ​​the target part;

[0058] The stress concentration area includes a first stress concentration area and a second stress concentration area. The first stress concentration area is a stress concentration area at the thin-wall inner cavity structure; the second stress concentration area is a stress concentration area at the outer wall structure.

[0059] The target part includes an outer wall structure and an inner cavity structure. The inner cavity structure is a thin-walled inner cavity structure, which has the characteristics of complexity, anisotropy, and thin-walled surface. The inner cavity of the target part is prohibited from modifying the structural design. The outer wall structure has a emergent surface structure and a small angle structure. The emergent surface structure includes but is not limited to cantilever, transverse circular hole, cross-section emergent and other structures. The small angle structure is a structure in which the angle between the planes perpendicular to the forming direction in the target part is less than 45°.

[0060] Before simulation, the following work needs to be done:

[0061] Conduct structural analysis on the target parts and select the best placement and forming angle, with stability, less support and short forming time as the basic principles.

[0062] Add process allowances to the target parts, including machining, grinding, and wire cutting allowances.

[0063] Add support structures according to the structural characteristics of the target part. For example, for areas that cannot be directly formed, such as emergent structures and small-angle structures, add solid sheet support to ensure that the part has no unformable structures. The premise of inner cavity printing is to ensure that there are no emergent surface structures and small-angle structures in the inner cavity.

[0064] The target parts after adding supports are simulated. During the printing process, the target parts will be affected by structure, stress, etc. to produce stress concentration areas, and the location of these areas will produce large deformations. These areas, namely stress concentration areas, can be displayed after simulation.

[0065] Step S2: adding auxiliary support in the first stress concentration area to obtain a first target part;

[0066] The operation of adding auxiliary support structure is performed in 3D software. Due to structural limitations, it is impossible to add support to the thin-walled inner cavity structure by referring to the outer shape. Only auxiliary support can be added to reduce the impact of deformation on the overall simulation.

[0067] Principles for adding auxiliary supports: (1) The inner cavity is a thin-walled structure with no deformation requirements, and there are no unformable structures, such as protruding surface structures, small-angle structures, etc. (2) The inner cavity structure is affected by the use environment and the internal structure cannot be adjusted. (3) The shape variable requirements of the outer surface are high, and the inner cavity is printed smoothly. (4) The simulated inner cavity structure is locally unstable during the anti-compensation process due to its thin wall and large stress concentration deformation, and it cannot reach the expected value and complete the structural optimization. (5) Auxiliary supports are used to ensure that it is a formable structure and do not add new risk points.

[0068] See also Figure 2 and Figure 3, the auxiliary support 2 is arranged on the surface of the thin-walled inner cavity structure 1, and the auxiliary support 2 is a rib with a certain thickness and width, forming a stable "+"-shaped structure. The auxiliary support structure can also form a stable "T"-shaped structure or other structures. When the auxiliary support 2 is suspended and vertical, the auxiliary support can be set to a self-forming angle, such as Figure 4 As shown, the side of the auxiliary support close to the bottom of the target part is an inclined surface, the angle a between the contact surface of the auxiliary support and the inclined surface is less than 40 degrees, and the contact surface is the surface in contact with the thin-walled inner cavity structure 1. The auxiliary support 2 is not connected to the outer wall structure to avoid affecting the simulation of the outer wall structure and ensure its accuracy.

[0069] By adding auxiliary supports in the first stress concentration area, local instability during the counter-compensation process can be avoided, and the counter-compensation of the outer wall structure can be ensured to proceed smoothly. After removal, the structure at the corresponding position can still be printed, thereby completing the structural optimization.

[0070] Step S3: using a counter-compensation method to adjust the first target part to obtain a second target part;

[0071] Before step S3, it is necessary to import the structure of the first target part except the auxiliary support into the anti-compensation software as a whole, and identify the separation area between the target part and the auxiliary support in the anti-compensation software; import the auxiliary support in the first target part into the separation area to complete the import of the first target part; this step can ensure that the auxiliary support is designated as support during the anti-compensation process, so that the part and the support are two separate individuals, which is convenient for the later export of the part.

[0072] Specifically, the above step S3 includes: taking the auxiliary support as the support point, adjusting the shape of the first stress concentration area in the first target part, changing the deformation direction of the first stress concentration area, until the first stress concentration area can be printed and formed when the auxiliary support is removed, thereby obtaining the second target part.

[0073] The operation of adjusting the shape of the first target part is performed in three-dimensional software.

[0074] Step S4: removing the auxiliary support in the second target part to obtain a target three-dimensional model of the target part;

[0075] The operation of removing auxiliary supports is performed in 3D software, and the output file is a 3D model.

[0076] Step S5: dividing the target three-dimensional model into regions and setting parameters according to preset rules to obtain a printing file; the energy density of the emergent surface structure of the target part in the printing file changes uniformly;

[0077] Energy density is mainly related to factors such as laser power, scanning speed, line spacing, layer thickness, etc. The energy density calculation formula is shown in formula (1):

[0078]

[0079] Where Eq is the energy density, P is the laser power, h is the scanning speed, v is the line spacing, and t is the layer thickness.

[0080] Specifically, step S5 divides the area of ​​the lower surface of the emergent surface structure that directly affects the forming quality and dimensional accuracy into zones, and adjusts parameters such as laser power, scanning speed, line spacing, and layer thickness in each zone to ensure the consistency of energy density and reduce the generation of residual stress, thereby optimizing the forming quality of the lower surface and obtaining higher dimensional accuracy.

[0081] Step S6: Printing the target part based on the printing file to obtain the target part.

[0082] The printing method is laser selective melting. After the parts are printed, wire cutting is used to separate the target parts from the substrate, and the outer surface of the target parts is ground, polished and sandblasted as a whole.

[0083] Through the above method, it can be known that the additive manufacturing method of a part provided by the present invention adds auxiliary support for the unstable structure of the inner cavity during the anti-compensation process, and directly removes it during the later printing process. It can greatly reduce the addition of outer wall control support without changing the design structure of the part, ensure the smooth completion of part optimization, shorten the printing cycle, reduce costs, and reduce the secondary deformation of the part to a certain extent. Through this method, parts with thin-walled inner cavity structures can be printed and formed without adding supports, greatly reducing the deformation of the parts. In addition, the target three-dimensional model is divided into regions and parameters are set according to preset rules to obtain a printing file; the energy density of the emergent surface structure in the printing file changes uniformly, avoiding the situation in which the material melts and solidifies rapidly during the laser selective melting process to produce a large temperature gradient, reducing the generation of residual stress, and thus avoiding the problem of warping and slag of the emergent surface structure under the action of residual stress. Further improve the printing accuracy and forming quality of the parts.

[0084] For parts with high requirements for outer wall structural deformation, it is necessary to perform local shape control on the locations with large deformation in the simulation results. For thin-walled and high parts, the conventional method of adding cross ribs or I-shaped ribs from top to bottom on the outer wall surface may result in a large weight of the added support, which greatly increases the cost.

[0085] Based on this, before step S3, the strength of the outer wall structure can be increased by adding oblique reinforcement on the wall. The specific method is as follows:

[0086] In the target part after adding the auxiliary support, determining a target outer wall structure in the second stress concentration region in which the wall thickness is less than a preset wall thickness threshold and the height is greater than a preset height threshold;

[0087] Here, height refers to the dimension along the forming direction.

[0088] A mesh support structure is added to the outer surface of the target outer wall structure to obtain a first target part.

[0089] like Figure 5 As shown, the mesh support structure 3 is composed of a plurality of interwoven oblique ribs, and the mesh of the mesh support structure 3 is in a diamond shape; the wall thickness of the oblique rib d≥1mm, preferably, the value of d is within the range of 1mm to 4mm; such as 1mm, 2mm, 3mm, 4mm, the angle between the oblique rib and the horizontal plane is greater than 50°, the horizontal plane is perpendicular to the forming direction, the spacing between two adjacent and parallel oblique ribs is greater than 10mm, a circular hole is added to the root of the oblique rib for easy removal later, the end of the oblique rib close to the bottom of the target part is set as a self-forming structure, and the angle between the bottom surface of the oblique rib and the forming direction is less than 40°.

[0090] As an optional method, the above step S5 can be implemented based on the following steps:

[0091] Step S51: Slicing the target three-dimensional model according to a first preset thickness to obtain a plurality of slice layers;

[0092] The area in the slice layer, above which there is no exposure area, is called the upper surface area; the area in the slice layer, below which there is no exposure area, is called the lower surface area; the inner surface area is the area between the "upper surface area" and the "lower surface area"; the lower surface area contains the emergent surface of the emergent surface structure of the part, and the emergent surface is the surface of the lower surface suspended, for example, Figure 6 As shown, the lower surface of the part is the emergent surface 4. The area division method of the present invention is to divide the lower surface area, and the division method is as follows.

[0093] Step S52: taking the emergent surface as the lower surface, segmenting the plurality of slice layers through a preset number of slice layers along the forming direction to obtain a target area;

[0094] The emergent surface is the lower surface of the emergent surface structure;

[0095] The number of layers of the target area finally obtained by division is set to N, and the first preset thickness of the slice layer is set to T, that is, the preset number of layers passed through is N, and the target area includes a first area and a second area; the first area is the area where the emergent surface is located, the number of layers of the first area is 1, and the layer thickness of the first area is the first preset thickness, and the second area is the area other than the first area in the target area, the number of layers of the second area is N-1, and the layer thickness of the second area is greater than or equal to the first preset thickness; optionally, for the same part, the number of layers of multiple target areas obtained by division may be different, because some parts of the part have a relatively large thickness of the emergent surface structure, and N layers of the target area can be obtained, and some parts have a relatively small thickness of the emergent surface structure, and N layers of the target area cannot be obtained, then the number of layers of the target area can be determined according to the specific thickness, and the target area obtained by dividing the emergent structure with a particularly small thickness may also include only one layer of the first area.

[0096] For example, Figure 7 As shown, the part has three emergent surfaces, the thickness of the slice layer is T, and three target areas can be obtained through the division method of step S52: area A, area B and area C, where the number of layers of area A and area B is 2, the first area of ​​area A is A1, and the second area is A2, the first area of ​​area B is B1, and the second area is B2, and area C only includes 1 layer of the first area C1.

[0097] Step S53: dividing the first region according to a preset region width along a direction perpendicular to the forming direction to obtain a plurality of first sub-regions, and dividing the second region according to the preset region width along a direction perpendicular to the forming direction to obtain a plurality of second sub-regions;

[0098] The number of the first sub-areas is the same as the number of the second sub-areas; the number of the first sub-areas and the number of the second sub-areas are related to the angle between the lower surface and the horizontal plane. The smaller the angle, the more sub-areas are divided, and the smaller the angle, the fewer sub-areas are divided. When the angle is 45°, the preset area width is the same as the first preset thickness. The sub-area division is also related to the part structure. For example, the suspension bridge structure does not need to be divided into sub-areas, and the cantilever structure is suitable for multiple sub-area divisions.

[0099] For example, Figure 8As shown, the area adjacent to area A1 in a direction perpendicular to the forming direction is the inner surface area. Area A1 is divided using the boundary line between the inner surface area and area A1 as the reference line. The dividing line 5 of each sub-area is parallel to the forming direction. The preset area width is b, and area A1 is divided into three first sub-areas. According to the direction away from the inner surface area and close to the edge of the part, the three first sub-areas are numbered in order from small to large: 1, 2, 3. For the first area and the second area in the same target area, the number of divided sub-areas and the preset area width of the divided area are the same, and the numbering method is also the same.

[0100] Step S54: setting parameters for the first sub-region and the second sub-region to obtain a first parameter solution;

[0101] Specifically, the parameters of the first sub-region and the second sub-region may be set according to the rule that the laser power is from large to small, the scanning speed is from slow to fast, and the line spacing is from small to large along the target direction.

[0102] In the first parameter scheme, the energy density of the second area in the same target area is greater than or equal to the energy density of the first area, and the energy density of the first sub-area gradually decreases along the target direction; the energy density of the second sub-area gradually decreases along the target direction, and the target direction is a direction perpendicular to the forming direction and close to the edge of the part; optionally, the energy density of two adjacent first sub-areas may also be the same, and the energy density of two adjacent second sub-areas may also be the same.

[0103] For example, Figure 8 As shown, the direction in which the number increases is the target direction. Along the direction in which the number increases, the energy density of the first sub-region gradually decreases, or the energy density of two adjacent first sub-regions is the same. Assuming that the energy density of region 1 is E1, the energy density of region 2 is E2, and the energy density of region 3 is E3, then E1≥E2≥E3.

[0104] like Figure 7 As shown, when the number of emergent surface structures is greater than 1 and the lower surfaces of different emergent surface structures are located in different slice layers, the same slice layer will include a first area and a second area. At this time, the first area and the second area belong to two different target areas. When setting the parameters, the energy density of the first area in the same slice layer in the first parameter scheme is made less than or equal to the energy density of the second area.

[0105] Step S54: setting parameters for the area in the slice layer except the target area to obtain a second parameter scheme; the first parameter scheme and the second parameter scheme constitute the printing file.

[0106] The second parameter scheme is set according to the conventional parameter setting method, which will not be described here.

[0107] In the actual additive manufacturing process, the setting of layer thickness is also an important factor affecting the printing quality of parts. For small-angle structures, if there is no support, only one slicing and layering process and printing may result in failure to form, or poor quality of printed parts. In order to improve the accuracy of part printing, the present invention also provides an implementation method, which continues to layer the first sub-region and the second sub-region on the basis of step S53, specifically:

[0108] The first sub-region and the second sub-region are layered according to a second preset thickness along a forming direction to obtain a first sub-region layering scheme and a second sub-region layering scheme;

[0109] The second preset thickness gradually decreases along the target direction, and the first preset thickness is an even multiple of the second preset thickness, that is, T=2nt i , where T is the first preset thickness, n is an integer greater than 0, t i is the second preset thickness of the i-th sub-region. The first sub-region layering scheme is that the second preset thickness corresponding to the first sub-region gradually decreases along the target direction; the second sub-region layering scheme is that the second preset thickness corresponding to the second sub-region gradually decreases along the target direction;

[0110] For example, Figure 7 The regions A1, A2, B1, B2, and C1 in the embodiment are layered according to the second preset thickness to obtain the following Fig. 9 In the stratification scheme shown, the stratification thickness of each sub-region decreases as the number increases; Fig. 9 As shown, T is the first preset thickness, t 1 ,t 2 ,t 3 is the second preset thickness, wherein t1 is the layer thickness of the first sub-region numbered 1 in the A1 region, t2 is the layer thickness of the first sub-region numbered 2 in the A1 region, t3 is the layer thickness of the first sub-region numbered 3 in the A1 region, and T≥t1≥t2≥t3.

[0111] See also Fig.10 , A1 is the first area, A2 is the second area, and the number of printed layers of each sub-area of ​​the first area and the second area is accumulated in the part forming direction. Each sub-area is numbered, and the numbering rule is: assuming that the number of layers N of the target area is 2, the number of printed layers of the sub-area numbered 3 of the first area is 4, and the number of printed layers of the sub-area numbered 3 of the second area is 4, and the total number is 8 layers, then the numbers of the 8 layers are: A1-03-01~04, A2-03-01~04.

[0112] After determining the layer thickness and the number of printing layers, the parameters of the first and second regions after layering are set according to the method of step S54. Finally, the target part is printed according to the first sub-region layering scheme, the second sub-region layering scheme and the parameter scheme obtained by the parameter setting to obtain the target part.

[0113] The parameters are set according to the rule that the laser power along the target direction is from large to small, the scanning speed is from slow to fast, and the line spacing is from small to large. Each layer in each sub-area can be set with different parameters or the same parameters, but the energy density of the first area should be ≤ the energy density of the second area.

[0114] The above method can realize setting different parameters such as area width, laser power, scanning speed, etc. according to different part structures or material characteristics; further stratify the sub-regions, and each sub-stratified region can set printing parameters such as laser power and scanning speed separately, or set the same parameters as other stratifications, and make the energy density decrease, reduce the temperature gradient, reduce the residual stress, improve the success rate of the part's emergent surface, and improve the printing quality of the emergent surface. It can be widely used in part structures with emergent surfaces, with high flexibility and strong practicality. In addition, the first sub-region and the second sub-region are further stratified, and the stratification scheme obtained is more refined. When printing, it is printed layer by layer. Due to the small layer thickness, the powder thickness and the powder amount are small, and the situation of excess liquid metal splashing and adhering to the overhanging surface is avoided. Improve the quality of printed parts.

[0115] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0116] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A method for additive manufacturing of a part, characterized in that: include: Simulating an additive manufacturing process of a target part to determine a stress concentration area of ​​the target part; The stress concentration region includes at least a first stress concentration region, and the first stress concentration region is a stress concentration region at a thin-wall inner cavity structure; Add auxiliary support in the first stress concentration area to obtain a first target part; The first target part is adjusted by using a counter-compensation method to obtain a second target part; removing the auxiliary support in the second target part to obtain a target three-dimensional model of the target part; Divide the target three-dimensional model into regions and set parameters according to preset rules to obtain a printing file; The energy density of the emergent surface structure of the target part in the printing file changes uniformly; The target part is printed based on the printing file to obtain the target part.

2. The additive manufacturing method of a part according to claim 1, characterized in that: The target three-dimensional model is divided into regions and parameters are set according to preset rules to obtain a print file, which includes: Slicing the target three-dimensional model according to a first preset thickness to obtain a plurality of slice layers; Taking the emergent surface as the lower surface, a plurality of slice layers are segmented through a preset number of slice layers along a forming direction to obtain a target area; the target area includes a first area and a second area; the first area is the area where the emergent surface is located, and the second area is the area of ​​the target area other than the first area; the layer thickness of the first area is the first preset thickness; the layer thickness of the second area is greater than or equal to the first preset thickness; the emergent surface is the lower surface of the emergent surface structure; The first region is divided according to a preset region width along a direction perpendicular to the forming direction to obtain a plurality of first sub-regions, and the second region is divided according to the preset region width along a direction perpendicular to the forming direction to obtain a plurality of second sub-regions; Parameters are set for the first sub-region and the second sub-region to obtain a first parameter scheme; in the first parameter scheme, the energy density of the second region is greater than or equal to the energy density of the first region, the energy density of the first sub-region gradually decreases along a target direction, and the energy density of the second sub-region gradually decreases along the target direction; the target direction is a direction perpendicular to a forming direction and close to an edge of a part; Parameters are set for the area in the slice layer except the target area to obtain a second parameter scheme; the first parameter scheme and the second parameter scheme constitute the printing file.

3. The additive manufacturing method of the part according to claim 2, characterized in that: The method further includes dividing the first region according to a preset region width along a direction perpendicular to the forming direction to obtain a plurality of first sub-regions, and dividing the second region according to the preset region width along a direction perpendicular to the forming direction to obtain a plurality of second sub-regions: The first sub-region and the second sub-region are layered according to the second preset thickness along the forming direction to obtain a first sub-region layering scheme and a second sub-region layering scheme; the first sub-region layering scheme is that the second preset thickness corresponding to the first sub-region gradually decreases along the target direction; the second sub-region layering scheme is that the second preset thickness corresponding to the second sub-region gradually decreases along the target direction; The target part is printed according to the first sub-region layering scheme and the second sub-region layering scheme to obtain the target part.

4. The additive manufacturing method of a part according to claim 2, characterized in that: Setting parameters for the first sub-region and the second sub-region to obtain a first parameter solution includes: The parameters of the first sub-area and the second sub-area are set according to the rule that the laser power is from large to small, the scanning speed is from slow to fast, and the line spacing is from small to large along the target direction to obtain a first parameter scheme.

5. The additive manufacturing method of a part according to claim 2, characterized in that: The number of the emergent surface structures is greater than 1 and the lower surfaces of different emergent surface structures are located in different slice layers; the energy density of the first area in the same slice layer in the first parameter scheme is less than or equal to the energy density of the second area.

6. The additive manufacturing method of a part according to claim 2, characterized in that: The energy density of two adjacent first sub-regions is equal, and the energy density of two adjacent second sub-regions is equal.

7. The additive manufacturing method of a part according to claim 1, characterized in that: The adopting the anti-compensation method to adjust the first target part to obtain the second target part comprises: With the auxiliary support as a supporting point, the shape of the first stress concentration area in the first target part is adjusted to change the deformation direction of the first stress concentration area until the first stress concentration area can be printed and formed when the auxiliary support is removed, thereby obtaining a second target part.

8. The additive manufacturing method of a part according to claim 1, characterized in that: The target part further includes an outer wall structure, the stress concentration area further includes a second stress concentration area, and the second stress concentration area is a stress concentration area at the outer wall structure; after adding auxiliary support to the first stress concentration area, the method further includes: In the target part after adding the auxiliary support, determining a target outer wall structure in the second stress concentration region whose wall thickness is less than a preset wall thickness threshold and whose height is greater than a preset height threshold; A mesh support structure is added to the outer surface of the target outer wall structure to obtain a first target part; the mesh support structure is composed of a plurality of mutually interwoven oblique ribs, and the meshes of the mesh support structure are in a diamond shape.

9. The additive manufacturing method of a part according to claim 1, characterized in that: The method of using the anti-compensation method to adjust the first target part to obtain the second target part also includes: Importing the structure of the first target part except the auxiliary support into the anti-compensation software as a whole, and identifying the separation area of ​​the target part and the auxiliary support in the anti-compensation software; Introducing the auxiliary support in the first target part into the separation area to complete the introduction of the first target part; The first target part is adjusted by using a counter-compensation method to obtain a second target part.

10. The additive manufacturing method of a part according to claim 1, characterized in that: A side of the auxiliary support close to the bottom of the target part is an inclined surface, an angle between a contact surface of the auxiliary support and the inclined surface is less than 40°, and the contact surface is a surface in contact with the thin-wall inner cavity structure.

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