A thin-walled curved surface porous part design method for laser selective melting technology

Abstract

The present application relates to a kind of thin-walled curved surface porous part design method for laser selective melting technology, specific steps include: S1, preparation thin-walled curved surface model;S2, construct fill cell;S3, curvature analysis is carried out to thin-walled curved surface model and optimize filling direction: the curvature analysis of thin-walled section is carried out to thin-walled curved surface structure in step S1, combine the short side filling vector n h Optimization and determine filling direction;S4, construct thin-walled curved surface porous model: construct the space dot matrix structure with cell body as porous unit, revise the geometric line surface relationship of cell dot matrix, based on filling scheme, carry out porous construction to thin-walled curved surface model by Boolean intersection operation;S5, additive manufacturing.The thin-walled curved surface porous part design method for additive manufacturing provided by the present application can solve the problem of laser selective melting thin-walled curved surface porous structure processing difficulty.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a design method for thin-walled curved porous parts for laser selective melting technology. Background Technology

[0002] Additive manufacturing is an incremental manufacturing technology that creates parts by stacking materials layer by layer. It offers higher processing efficiency than traditional machining techniques in forming complex curved structures and is currently mainly used in aerospace, biomedicine, and automotive parts manufacturing. Its unique layer-by-layer stacking processing characteristics give additive manufacturing a unique advantage in the precision manufacturing of porous structures, enabling the formation of parts with micron-level pore features.

[0003] Currently, methods for representing porous structures are mainly divided into three categories: discrete voxel representation, parametric representation, and implicit function representation. Discrete voxel representation forms porous structures by regulating the density distribution on a global voxel mesh in three-dimensional space. The porous structure of the geometric model is expressed through discrete point values, and it is mainly used in topology optimization. The implicit function method can define any point value of the porous model, expressing various existing porous elements with mathematical functions, and constructing porous structures with multiple composite configurations by combining functions. Parametric representation is a mainstream CAD modeling method, possessing some integrated parametric geometric prototypes (such as spheres, cylinders, cuboids, beam elements, etc.). Based on these basic elements, porous elements can be constructed and porous structures can be represented. Currently, parametric porous model construction has the following drawbacks: the parametric representation method results in a lot of redundant geometric data after the porous element combination, and it can only perform porous Boolean operations on simple models. Thin-walled curved porous structures are widely used in fields such as oral guided bone regeneration. They generally have complex curved surfaces and thin walls of less than 1 mm. Their parametric porous models are difficult to construct using Boolean operations. Furthermore, the thin-walled characteristics result in low cell integrity and low structural strength of porous thin-walled curved structures, making them difficult to process. Summary of the Invention

[0004] Based on this, the present invention provides a design method for thin-walled curved porous parts for additive manufacturing, which solves the problem of difficult processing of thin-walled curved porous structures by selective laser melting.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A design method for thin-walled curved porous parts for laser selective melting technology includes the following steps:

[0007] S1. Prepare thin-walled surface model: Model the thin-walled surface or obtain a solid model using 3D scanning;

[0008] S2. Constructing the Filled Unit Cell: Design a porous filled unit cell based on the performance requirements of the thin-walled curved surface structure. Combined with a manufacturing process parameter library, construct the parametric model of the filled unit cell, analyze the boundary rectangle of the unit cell, and determine the short-side filling vector n of the unit cell. h ;

[0009] S3. Perform curvature analysis and optimize the filling direction for the thin-walled surface model: Perform curvature analysis on the thin-walled cross-section of the thin-walled surface structure in step S1, combined with the short-side filling vector n of the unit cell. h Optimize and determine the fill direction;

[0010] S4. Construct a thin-walled curved porous model: Construct a spatial lattice structure with unit cells as porous units, correct the geometric line-plane relationship of the unit cell lattice, and construct the porous thin-walled curved model through Boolean intersection operation based on the filling scheme;

[0011] S5. Additive Manufacturing: Using laser selective melting technology, after importing the thin-walled curved porous model, it is placed according to the principle of small Z-axis height. The support type of the thin-walled curved porous model is conical. The processing laser power, spot diameter, slice thickness, and conical support parameters are set to complete the additive manufacturing.

[0012] Preferably, in step S1, the thickness of the thin-walled curved surface model is 0.4 mm to 1.0 mm.

[0013] Preferably, in step S1, the thickness of the thin-walled surface is kept consistent at all points in the thin-walled surface model.

[0014] Preferably, in step S1, the thin-walled curved surface model is represented using a triangular mesh in STL file format.

[0015] Preferably, in step S2, the boundary rectangle of the analyzed unit cell is used to determine the short side filling vector n of the unit cell. h Specifically, this involves performing dimensional analysis on each boundary rectangle of the unit cell to determine the boundary rectangle with the shortest characteristic dimension. The direction vector of the shortest side of the boundary rectangle is the short side filling vector n. h .

[0016] Preferably, in step S3, the specific steps for curvature analysis and optimization of the fill direction are as follows:

[0017] a. Analyze the thin-walled cross-section of the thin-walled curved surface structure. Based on the unit cell filling spacing, equidistant points are selected on the curved edge, and the normal vector n of each point is used as the reference. t Characterize the curvature of the curved section;

[0018] b. For a single unit cell, the direction vector n of the shortest side of its boundary rectangle is... h The normal vector n of the curved edge tThey coincide, at this time n h With n t The included angle, i.e., the optimization angle α = 0°, achieves the optimal filling effect;

[0019] c. For multiple unit cells, the direction vector n of each unit cell h With the curvilinear normal vector n t There exists an optimization angle α for all n unit cells. Let the average optimization angle of the n unit cells be denoted as α.

[0020] d. Compare the various filling schemes and select the average optimal angle. The minimum filling scheme.

[0021] Preferably, in step S4, the construction of the porous model of the curved surface includes geometric line and surface correction of the lattice, unit cell array, and Boolean operation, specifically including the following steps:

[0022] a'. Measure the boundary rectangle of the thin-walled curved surface structure based on the filling scheme, and determine the number of unit cells to be filled according to the characteristic dimensions of the unit cell;

[0023] b' Perform triangular patch detection on the unit cell, including gaps, interfering shells, holes, bad edges, overlapping and intersecting triangular patches, and repair overlapping lines and surfaces and intersecting shells generated by the unit cell under parametric modeling;

[0024] c'. Perform XY plane array with unit cells as units, repeat the geometric line and surface correction process, detect and repair the triangular facets of the plane lattice, then perform spatial array in the Z-axis direction and detect and repair the geometric line and surface relationship of the lattice again.

[0025] d' Import the thin-walled curved surface STL model and perform Boolean intersection operation based on the filling scheme and spatial lattice structure;

[0026] e', Inspect and repair the thin-walled curved porous model.

[0027] Preferably, in step S5, the power range of the processing laser is 60W to 80W.

[0028] Preferably, in step S5, the diameter of the light spot ranges from 0.03 mm to 0.07 mm.

[0029] Preferably, in step S5, the slice thickness is 0.02 mm to 0.06 mm.

[0030] Preferably, in step S5, when placing the model based on the principle of small Z-axis height, model overlap in the Z-axis direction is avoided or reduced. When there is model curling overlap, the support of the upper overlapping part needs to be tilted by 1° to 3° and supported on the node of the lower overlapping part to avoid passing through the hole.

[0031] Preferably, after step 5, the following steps are also included:

[0032] S6. After completing additive manufacturing, the support is disassembled, wherein the support connected to the thin-walled curved structure at both ends is cut in the middle to facilitate the disassembly of the support from the thin-walled curved structure.

[0033] Compared with existing technologies, this invention provides a method for constructing complex thin-walled curved porous structures by repairing line-plane relationships and then performing Boolean operations. It also provides a method for optimizing the filling angle to prepare thin-walled porous structures with a wall thickness of less than 1 mm. The thin-walled curved porous structures fabricated using this method can retain the integrity of the filled unit cells to a greater extent, resulting in higher formability and stability (direct filling methods have high unit cell incompleteness). This overcomes the problems of difficult forming and low structural integrity of thin-walled curved porous structures in existing technologies. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of a design method for thin-walled curved porous parts for laser selective melting technology according to the present invention.

[0035] Figure 2 This is a schematic diagram illustrating the principle of optimizing the filling direction of a single regular octahedral cell in Embodiment 1 of the present invention.

[0036] Figure 3 This is a schematic diagram of the optimized filling scheme of multiple regular octahedral cells in Embodiment 1 of the present invention;

[0037] Figure 4 This is a schematic diagram illustrating the principle of optimizing the filling direction of a single tetrahedral unit cell in Embodiment 2 of the present invention.

[0038] Figure 5 This is a schematic diagram illustrating the optimization of multiple tetrahedral cell filling schemes in Embodiment 2 of the present invention. Detailed Implementation

[0039] To better understand the above-mentioned objectives, features, and advantages of the present invention, a preferred description of the present invention is provided below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0041] The preferred embodiments of the present invention will now be explained in conjunction with the accompanying drawings.

[0042] Example 1

[0043] like Figure 1 As shown, a design method for thin-walled curved porous parts for laser selective melting technology is presented. The method includes constructing a thin-walled curved surface model, constructing an infill unit cell, performing curvature analysis on the thin-walled curved surface model and optimizing the infill direction, constructing a porous model of the thin-walled curved surface structure, and additive manufacturing. The specific steps are as follows:

[0044] S1. After processing with 3D scanning, a thin-walled curved surface structure model is obtained, and the model is finally expressed in '.STL' format. The wall thickness of the thin-walled curved surface structure is 0.5mm.

[0045] S2. Select a regular octahedron as the filling unit cell, and combine it with manufacturing process parameters to complete the parametric model construction of the filling unit cell, the structure of which is as follows: Figure 2 As shown. Its boundary dimensions are 1mm×1mm×1.3mm, the diameter of the support column is 0.3mm, and the diameter of the inner hole is 0.4mm.

[0046] Among them, the boundary rectangle with the shortest characteristic dimension of the regular octahedron is determined. There are two types of boundary rectangles with the shortest side of the regular octahedron. Let n be the direction vector of the shortest side in the same plane of the two boundary rectangles. h1 n h2 .

[0047] S3. Perform curvature analysis of the thin-walled cross-section of the thin-walled curved surface structure in step S1, combined with the filling vector n of the unit cell. h The specific steps to optimize and determine the filling scheme are as follows:

[0048] a. Analyze the thin-walled curved surface structure and select the characteristic wall thickness section of the model.

[0049] b, such as Figure 2 As shown, for a single regular octahedron, the direction vector nh of the shortest side of its boundary rectangle and the normal vector n of the curved side are... t They coincide, at this time n h With n t The angle between the two points is the optimization angle α = 0°, which achieves the best filling effect.

[0050] c. For example Figure 3 As shown in Scheme A, for filling multiple regular octahedrons, the direction vector n of each regular octahedron is... h1 n h2 Its corresponding curvilinear normal vector n t Angle α exists in both cases. 1i α 2i Let the smaller value be α. i Let the average optimized angle of n regular octahedral unit cells be . but:

[0051]

[0052] d. Compare the various filling schemes and select the average optimal angle. The minimum fill scheme, such as Figure 3 As shown in Option B.

[0053] S4. Construct a space lattice structure with regular octahedrons as unit cells, fill the thin-walled curved surface structure based on the filling scheme, and construct a porous model of the thin-walled curved surface through geometric line and surface correction of the lattice and Boolean operations.

[0054] The specific steps are as follows:

[0055] a'. Measure the boundary rectangle of the thin-walled curved surface structure based on the filling scheme, and determine the number of unit cells to be filled according to the characteristic dimensions of the unit cell.

[0056] b' Perform triangular patch detection on the unit cell, including gaps, interfering shells, holes, bad edges, overlapping and intersecting triangular patches, etc., and repair overlapping lines and surfaces and intersecting shells generated by the unit cell under parametric modeling.

[0057] c'. Perform XY plane array with unit cells as units, repeat the geometric line and surface correction process, detect and repair the triangular facets of the planar lattice, then perform spatial array in the Z-axis direction and detect and repair the geometric line and surface relationship of the lattice again.

[0058] d' Import the thin-walled curved surface STL model and perform Boolean intersection operation based on the filling direction and the spatial lattice structure.

[0059] e', Inspect and repair the thin-walled curved porous model.

[0060] S5. Using laser selective melting manufacturing technology, after importing the model, it is placed according to the principle of small Z-axis height. The support type of the thin-walled curved porous model is conical. The processing laser power is set to 60W, the spot diameter is 0.05mm, the slice thickness is 0.03mm, and the upper and lower diameters of the conical support are 0.2mm. After completing the additive manufacturing with zinc, the support is disassembled.

[0061] When placing models based on the principle of small Z-axis height, model overlap in the Z-axis direction should be avoided or minimized as much as possible. If model curling and overlap still exist, the support of the upper overlapping part should be tilted at a certain angle (less than 3°) and supported by the node of the lower overlapping part to avoid passing through the hole. The supports connected to the structure at both ends are easier to remove after being shortened in the middle.

[0062] Example 2

[0063] like Figure 1As shown, a design method for thin-walled curved porous parts for laser selective melting technology is presented. The method includes constructing a thin-walled curved surface model, constructing an infill unit cell, performing curvature analysis on the thin-walled curved surface model and optimizing the infill direction, constructing a porous model of the thin-walled curved surface structure, and additive manufacturing. The specific steps are as follows:

[0064] S1. Model the thin-walled curved surface structure and finally express the model in '.STL' format. The wall thickness of the thin-walled curved surface structure is 0.4mm.

[0065] S2. Select a regular tetrahedron as the filling unit cell, and based on the manufacturing process parameters, complete the parametric model construction of the filling unit cell, with the structure as follows: Figure 4 As shown. Its boundary dimensions are 0.90mm × 0.81mm × 0.77mm, the diameter of the support column is 0.3mm, and the diameter of the inner hole is 0.3mm.

[0066] Specifically, the boundary rectangle with the shortest characteristic dimension of the regular tetrahedron is determined. For the regular octahedron, there exists a boundary rectangle with the shortest side. The direction vector of the shortest side of this boundary rectangle in the same plane is denoted as n. h1 n h2 .

[0067] S3. Perform curvature analysis of the thin-walled cross-section of the thin-walled curved surface structure in S1, combined with the filling vector n of the unit cell. h The specific steps to optimize and determine the filling scheme are as follows:

[0068] a. Analyze the thin-walled curved surface structure and select the characteristic wall thickness section of the model.

[0069] b, such as Figure 4 As shown, for a single regular tetrahedron, the direction vector n of the shortest side of its boundary rectangle is... h With the curvilinear normal vector n t They coincide, at this time n h With n t The angle between the two points is the optimization angle α = 0°, which achieves the best filling effect.

[0070] c. For example Figure 5 As shown in Scheme A, for multiple tetrahedral fillings, the direction vector n of each tetrahedral is... h1 n h2 Its corresponding curvilinear normal vector n t Angle α exists in both cases. 1i α 2i Let the smaller value be α. i Let the average optimized angle of n regular octahedral unit cells be . but:

[0071]

[0072] d. Compare the various filling schemes and select the average optimal angle. The minimum fill scheme, such as Figure 5 As shown in Option B.

[0073] S4. Construct a space lattice structure with regular tetrahedrons as unit cells, fill the thin-walled curved surface structure based on the filling scheme, and construct a porous model of the thin-walled curved surface through geometric line and surface correction of the lattice and Boolean operations.

[0074] The specific steps are as follows:

[0075] a'. Measure the boundary rectangle of the thin-walled curved surface structure based on the filling scheme, and determine the number of unit cells to be filled according to the characteristic dimensions of the unit cell.

[0076] b' Perform triangular patch detection on the unit cell, including gaps, interfering shells, holes, bad edges, overlapping and intersecting triangular patches, etc., and repair overlapping lines and surfaces and intersecting shells generated by the unit cell under parametric modeling.

[0077] c'. Perform XY plane array with unit cells as units, repeat the geometric line and surface correction process, detect and repair the triangular facets of the planar lattice, then perform spatial array in the Z-axis direction and detect and repair the geometric line and surface relationship of the lattice again.

[0078] d' Import the thin-walled curved surface STL model and perform Boolean intersection operation based on the filling direction and the spatial lattice structure.

[0079] e', Inspect and repair the thin-walled curved porous model.

[0080] S5. Using laser selective melting manufacturing technology, after importing the model, it is placed according to the principle of small Z-axis height. The support type of the thin-walled curved porous model is conical. The processing laser power is set to 80W, the spot diameter is 0.07mm, the slice thickness is 0.06mm, and the upper and lower diameters of the conical support are 0.2mm. After completing the additive manufacturing with zinc, the support is disassembled.

[0081] When placing models based on the principle of small Z-axis height, it is important to avoid or minimize model overlap in the Z-axis direction. If model curling and overlap still exist, the support of the upper overlapping part should be tilted at a certain angle (less than 3°) and supported by the node of the lower overlapping part to avoid passing through the hole. The supports connected to the structure at both ends are easier to remove after being shortened in the middle.

[0082] Finally, it should be noted that the above description is merely a technical example of the present invention and does not limit the invention. Those skilled in the art should understand that various changes can be made in form and detail. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

[0083] 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.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A design method for thin-walled curved porous parts for laser selective melting technology, characterized in that, Includes the following steps: S1. Prepare thin-walled surface model: Model the thin-walled surface or obtain a solid model using 3D scanning; S2. Constructing the Filled Unit Cell: Design a porous filled unit cell based on the performance requirements of the thin-walled curved surface structure. Combined with a manufacturing process parameter library, construct the parametric model of the filled unit cell, analyze the boundary rectangle of the unit cell, and determine the short-side filling vector n of the unit cell. h ; S3. Perform curvature analysis and optimize the filling direction for the thin-walled surface model: Perform curvature analysis on the thin-walled cross-section of the thin-walled surface structure in step S1, combined with the short-side filling vector n of the unit cell. h Optimize and determine the fill direction; S4. Construct a thin-walled curved porous model: Construct a spatial lattice structure with unit cells as porous units, correct the geometric line-plane relationship of the unit cell lattice, and construct the porous thin-walled curved model through Boolean intersection operation based on the filling scheme; S5. Additive Manufacturing: Using laser selective melting technology, after importing the thin-walled curved porous model, it is placed according to the principle of small Z-axis height. The support type of the thin-walled curved porous model is conical. The processing laser power, spot diameter, slice thickness, and conical support parameters are set to complete the additive manufacturing.

2. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S1, the thickness of the thin-walled curved surface model is 0.4 mm to 1.0 mm.

3. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S1, the thickness of the thin-walled surface remains consistent throughout the thin-walled surface model.

4. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S1, the thin-walled curved surface model is represented using a triangular mesh in STL file format.

5. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S2, the boundary rectangle of the analyzed unit cell is used to determine the short side filling vector n of the unit cell. h Specifically, this involves performing dimensional analysis on each boundary rectangle of the unit cell to determine the boundary rectangle with the shortest characteristic dimension. The direction vector of the shortest side of the boundary rectangle is the short side filling vector n. h .

6. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S3, the specific steps for curvature analysis and optimization of the fill direction are as follows: a. Analyze the thin-walled cross-section of the thin-walled curved surface structure. Based on the unit cell filling spacing, equidistant points are selected on the curved edge, and the normal vector n of each point is used as the reference. t Characterize the curvature of the curved section; b. For a single unit cell, the direction vector n of the shortest side of its boundary rectangle is... h The normal vector n of the curved edge t They coincide, at this time n h With n t The included angle, i.e., the optimization angle α = 0°, achieves the optimal filling effect; c. For multiple unit cells, the direction vector n of each unit cell h With the curvilinear normal vector n t There exists an optimization angle α for all n unit cells. Let the average optimization angle of the n unit cells be denoted as α. d. Compare the various filling schemes and select the average optimal angle. The minimum filling scheme.

7. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S4, the construction of the porous model of the curved surface includes geometric line and surface correction of the lattice, unit cell array, and Boolean operations, specifically including the following steps: a'. Measure the boundary rectangle of the thin-walled curved surface structure based on the filling scheme, and determine the number of unit cells to be filled according to the characteristic dimensions of the unit cell; b' Perform triangular patch detection on the unit cell, including gaps, interfering shells, holes, bad edges, overlapping and intersecting triangular patches, and repair overlapping lines and surfaces and intersecting shells generated by the unit cell under parametric modeling; c'. Perform XY plane array with unit cells as units, repeat the geometric line and surface correction process, detect and repair the triangular facets of the plane lattice, then perform spatial array in the Z-axis direction and detect and repair the geometric line and surface relationship of the lattice again. d' Import the thin-walled curved surface STL model and perform Boolean intersection operation based on the filling scheme and spatial lattice structure; e', Inspect and repair the thin-walled curved porous model.

8. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S5, the power range of the processing laser is 60W to 80W; The diameter of the light spot ranges from 0.03 mm to 0.07 mm; The thickness of the slice is 0.02 mm to 0.06 mm.

9. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, In step S5, based on the placement principle of small Z-axis height, model overlap in the Z-axis direction should be avoided or reduced. When there is model curling overlap, the support of the upper overlapping part should be tilted by 1° to 3° and supported on the node of the lower overlapping part to avoid passing through the hole.

10. The design method for thin-walled curved porous parts for laser selective melting technology according to claim 1, characterized in that, Following step S5, the following steps are also included: S6. After completing additive manufacturing, the support is disassembled, wherein the support connected to the thin-walled curved structure at both ends is cut in the middle to facilitate the disassembly of the support from the thin-walled curved structure.

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