Shape design method and shape design program

Abstract

To design an additively manufactured body that has strength equivalent to that of a desired injection-molded body. [Solution] The shape design method includes the steps of: dividing the shape of an anisotropic additive manufacturing body into an invariant region where shape changes are not permitted and a variable region where shape changes are permitted; designing the resulting variable region based on the rigidity of an injection molded body having the same shape as the anisotropic additive manufacturing body; performing structural analysis calculations using a structural analysis model of the additive manufacturing body obtained by combining the designed variable region and the invariant region; and determining whether the rigidity and strength of the additive manufacturing body obtained by the structural analysis calculations are within an acceptable range.

Description

[Technical Field]

[0001] This disclosure relates to a shape design method and a shape design program. [Background technology]

[0002] In general, anisotropic injection-molded articles obtained by injection molding thermoplastic resins or thermoplastic resin compositions are widely used, for example, as industrial products. Such anisotropic injection-molded articles are required to be manufactured to conform to the shape specified in the design drawings in order to perform their function as industrial products. Therefore, when manufacturing anisotropic injection-molded articles by injection molding, mold manufacturing takes time, and dimensional stability problems such as warping can occur.

[0003] Therefore, in recent years, there has been research into using 3D printers to manufacture prototypes and products of structures made from thermoplastic resins or thermoplastic resin compositions, thereby significantly shortening the lead time for design and manufacturing. Specifically, it is being considered that, for example, molten thermoplastic resin can be extruded from the extrusion head of a 3D printer to form layers corresponding to the cross-sectional shape of the desired structure, and then these layers can be stacked to manufacture the structure as an anisotropic additively fabricated body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-109401 [Patent Document 2] Japanese Patent Publication No. 2017-177462 [Patent Document 3] Japanese Patent Publication No. 2021-028164 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when manufacturing additively manufactured objects using a 3D printer, there is a problem in that it is not easy to design the shape of an additively manufactured object that has the same strength as an injection-molded object, because the physical properties depend on the printing path (toolpath), which is the movement path of the extrusion head. In other words, because the physical properties such as rigidity and strength of an anisotropic additively manufactured object change depending on the printing path, the rigidity and strength may not be the same even if the shape is the same as an injection-molded object. For this reason, when designing strength using numerical analysis, it is difficult to design an additively manufactured object that has the same shape as an injection-molded object and also has the same rigidity and strength as an injection-molded object.

[0006] The technology disclosed herein has been made in view of the above, and aims to provide a shape design method and a shape design program that can design an additively manufactured body having strength equivalent to that of a desired injection molded body. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a shape design method includes the steps of: dividing the shape of an anisotropic additively manufactured body into an invariant region in which no change in shape is permitted and a variable region in which change in shape is permitted; designing the resulting variable region based on the rigidity of an injection-molded body having the same shape as the anisotropic additively manufactured body; performing a structural analysis calculation using a structural analysis model of the additively manufactured body obtained by combining the designed variable region and the invariant region; and determining whether the rigidity and strength of the additively manufactured body obtained by the structural analysis calculation are within an acceptable range.

[0008] Furthermore, according to another aspect of the present disclosure, the shape design program causes a computer to perform the following steps: divide the shape of an anisotropic additively manufactured body into an invariant region in which no change in shape is permitted and a variable region in which change in shape is permitted; design the resulting variable region based on the rigidity of an injection-molded body having the same shape as the anisotropic additively manufactured body; perform a structural analysis calculation using a structural analysis model of the additively manufactured body obtained by combining the designed variable region and the invariant region; and determine whether the rigidity and strength of the additively manufactured body obtained by the structural analysis calculation are within an acceptable range. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a flowchart showing a shape design method according to one embodiment. [Figure 2] Figure 2 shows a specific example of domain partitioning. [Figure 3] Figure 3 is a flowchart showing the variable domain design steps. [Figure 4] Figure 4 shows a specific example of how to conduct a bending test. [Figure 5] Figure 5 shows the boundary conditions for Example 1. [Figure 6] Figure 6 shows the element density distribution according to Example 1. [Figure 7] Figure 7 shows the design results for Example 1. [Figure 8] Figure 8 shows the deformation distribution related to Example 1. [Figure 9] Figure 9 shows the shape of the variable region according to Example 2. [Figure 10] Figure 10 shows the boundary conditions for Example 2. [Figure 11] Figure 11 shows the shape of the additively manufactured body according to Example 2. [Figure 12] Figure 12 shows the deformation distribution related to Example 2. [Figure 13]FIG. 13 is a block diagram showing an example of the hardware configuration of an information processing apparatus. [Embodiment for Carrying out the Invention]

[0010] Hereinafter, an embodiment according to the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples and are not to be construed as being limited by this description.

[0011] [Shape Design Method of Anisotropic Laminated Structure Body] FIG. 1 is a flowchart showing a shape design method of an anisotropic laminated structure body according to an embodiment. Generally, when manufacturing an anisotropic laminated structure body using a 3D printer, for example, a shaping method such as the material extrusion method (MEX: Material EXtrusion) is used. In the fused filament fabrication (FFF), which is a kind of material extrusion method, a filamentous thermoplastic resin is used, the thermoplastic resin is melted by a filament heating device, the melted single-fiber resin is discharged from a discharge head to form a layer, and the laminated structure body is created by laminating these layers. Also, an anisotropic laminated structure body may be created by a method of melting pellet-shaped thermoplastic resin without using a filament. The shape design method shown in FIG. 1 designs the shape of this anisotropic laminated structure body.

[0012] As shown in FIG. 1, the shape design method according to an embodiment includes a step of obtaining the rigidity and strength of an injection molded body (step S101), a step of region-dividing the shape of a product (step S102), a step of designing the shape of a variable region (step S103), a step of creating the shape of a laminated structure body (step S104), a step of performing a structural analysis calculation of the laminated structure body (step S105), and a step of determining the rigidity and strength of the laminated structure body (step S106).

[0013] [Step of Obtaining Rigidity and Strength of Injection Molded Body (Step S101)] In the step of obtaining the rigidity and strength of the injection-molded product, the rigidity and strength of the injection-molded product are obtained when the product to be manufactured is produced by injection molding.

[0014] Specifically, the rigidity and strength of injection-molded parts are obtained from products manufactured by injection molding, or from CAD information at the conceptual and design stages. That is, if an actual product exists, a universal testing machine is used under the desired constraint, load, and deformation conditions, and the rigidity and strength are obtained from the load / displacement curve. In this case, since the rigidity and strength may change depending on the test location and test conditions, the test location and test conditions are set according to the required product characteristics.

[0015] On the other hand, if there are no actual products manufactured by injection molding, the stiffness and strength of the injection-molded body can be predicted, for example, by CAE analysis. When isotropic materials are used and the load and displacement are small, static linear structural analysis using catalog data is sufficient. However, when anisotropy is considered, it is preferable to determine the anisotropy by, for example, injection molding CAE analysis using the finite element method. Furthermore, even when isotropic materials are used, if the load and displacement are large, structural analysis considering nonlinearity may be performed. In any case, data corresponding to the stiffness and strength of the injection-molded body is obtained and used as a design guideline for additively manufactured bodies.

[0016] [Region division step (step S102)] In the region division step, the shape of the product to be manufactured is divided into an immutable region where shape changes are not permitted and a variable region where shape changes are permitted.

[0017] Specifically, within the product shape, areas including the design surface and areas where the shape cannot be changed considering the product's function are set as unchanging areas, while areas that can be deleted to create a hollow portion are set as variable areas. That is, for example, as shown in Figure 2, the product shape 10 is divided into an unchanging area 11 that includes the exterior and cannot be deleted, and a variable area 12 where it is permissible to change the shape by deleting at least a part of it.

[0018] Furthermore, if the invariant region is excessively large, it may be difficult to reproduce the same rigidity and strength as an injection-molded part using additive manufacturing. However, there is no problem if the invariant region is small or nonexistent. Also, in the case of shapes with so-called undercuts (shapes where parts are hidden when the product is viewed from one direction), it becomes necessary to support the undercut portion with support material during additive manufacturing, which increases the manufacturing cost. For this reason, it is desirable to set the invariant region so as not to include the undercut portion.

[0019] [Variable region design step (Step S103)] In the variable region design step, the solid and hollow regions within the variable region are determined based on the rigidity of the injection-molded body and the additively manufactured body.

[0020] The determination of which regions within the variable region will be solid regions filled with resin and which regions will be hollow regions not filled with resin is made by methods such as a first method, which calculates the element density using a phase optimization method and determines the solid and hollow regions from the element density, or a second method, which calculates the cross-sectional area ratio that the cross-sectional area of ​​the solid portion and the cross-sectional area of ​​the hollow portion must satisfy from the rigidity of the product shape and determines the solid and hollow regions to satisfy the cross-sectional area ratio.

[0021] The specific process of the variable region design step (step S103) will be described in detail later.

[0022] [Additive manufacturing shape creation step (Step S104)] In the additive manufacturing shape creation step, the variable region designed in the variable region design step (step S103) is combined with the invariant region to create the shape of the additive manufacturing body.

[0023] In other words, the shape of the additively manufactured object, which corresponds to the shape of the product, is created when the determined hollow region is removed and the variable region is combined with the invariant region.

[0024] [Structural Analysis Calculation Step (Step S105)] In the structural analysis calculation step, structural analysis calculations are performed on the shape of the additively manufactured body, and the stiffness and strength of the additively manufactured body are calculated.

[0025] Specifically, the shape of the created additively fabricated object is divided into micro-regions to create a finite element model, and boundary conditions such as constraint conditions, load conditions, and deformation conditions are set, after which the stiffness and strength of the additively fabricated object are calculated. In this structural analysis calculation, anisotropic material properties based on the fabrication path may be input, and calculations using anisotropic material properties may be performed.

[0026] [Step for determining the rigidity and strength of the additively manufactured object (Step S106)] In the step for determining the rigidity and strength of the additively manufactured body, the rigidity and strength of the additively manufactured body calculated by structural analysis are compared with the rigidity and strength of the injection-molded body to determine whether or not they are within the acceptable range.

[0027] If the rigidity and strength of the additively manufactured body are not within the acceptable range as a result of this determination (step S106No), the process is repeated starting from the setting of the invariant region and the variable region. That is, if the rigidity and strength of the additively manufactured body differ significantly from those of the injection-molded body, the settings of the invariant region and the variable region are changed, and the design of the variable region is performed again. On the other hand, if the rigidity and strength of the additively manufactured body are within the acceptable range (step S106Yes), the process ends, as it is assumed that an additively manufactured body with rigidity and strength equivalent to that of the injection-molded body has been designed.

[0028] Next, the specific processing of the variable region design step (step S103) described above will be explained. As mentioned above, in the variable region design step, the shape of the variable region is designed by either a first method using a phase optimization method or a second method using a cross-sectional area ratio.

[0029] Figure 3 is a flowchart illustrating the first method using the phase optimization method.

[0030] First, both the invariant and variable regions of the product's shape are divided into minute regions, and a model necessary for performing the topology optimization method is created (step S201). Specifically, for example, the product shape is imported into a computer using a CAD interface, or the shape of the injection molded part is created by a CAD system and the modeling range is set. Then, element division is performed using a finite element method or the like by an element division preprocessor, and each of the invariant and variable regions is divided into multiple regions, and a model for topology optimization is created.

[0031] The element shape can be selected from options such as tetrahedral linear elements, quadratic elements, hexahedral linear elements, quadratic elements, etc. In step S101 above, if the rigidity and strength of the injection-molded body are predicted by CAE analysis, the element shape may be selected according to the specifications of the finite element method software, the specifications of the computer system, and the computational cost. Furthermore, high computational accuracy cannot be obtained if the number of element divisions is not sufficiently fine, while in the topology optimization method, the calculation is repeated multiple times, so it is preferable to have fewer elements in the finite element model. Therefore, a suitable number of element divisions should be determined appropriately, taking into account the required computational accuracy and computation time.

[0032] In this example, a finite element model is used as the model for topology optimization. However, the results of other CAE analyses, such as finite difference analysis or meshless analysis, can also be used to obtain a model for topology optimization.

[0033] Once the model for topological optimization is created, boundary conditions for the topological optimization calculation are set (step S202). Specifically, in addition to constraint conditions, load conditions, and deformation conditions, Young's modulus and Poisson's ratio are set, and furthermore, the objective function and constraint conditions for the topological optimization calculation are set.

[0034] The objective function used is compliance, which is the reciprocal of the stiffness of the additively manufactured object. In the topology optimization calculation, the element density is determined to minimize the compliance, which is the objective function. The constraint is the contribution rate, which represents the degree to which the deformation of each element contributes to the deformation of the overall product shape. The topology optimization calculation is performed under the constraint that the contribution rate satisfies predetermined conditions. The contribution rate can be defined as [1 - (volume that can be removed while satisfying the constraint / volume of the original shape)].

[0035] The threshold value indicating the conditions that the contribution rate must satisfy can be set appropriately according to, for example, the required accuracy of the analysis. However, here, the objective is not to reduce the contribution rate, but to make the rigidity and strength of the injection-molded body and the additively manufactured body equivalent. Therefore, the value α shown in equation (1) below is used.

number

[0036] The correction coefficient f is the Young's modulus E inj , E mex This setting is used to account for differences between the product shape required when a specific shape is needed and the shape of the injection-molded part, as well as constraint conditions, load conditions, and deformation conditions.

[0037] Once boundary conditions are set, a topological optimization calculation is performed (step S203). Specifically, boundary conditions are set for the model used for topological optimization, and optimization is performed to minimize the compliance, which is the objective function, under constraints on the contribution rate. In this topological optimization calculation, mathematical programming methods such as Homogenization Design Method (HDM), Density Approach, Genetic Algorithm, Simulated Annealing, Cellular Automata, or Level Set Method can be used.

[0038] The result of the topological optimization calculation is expressed as the element density for each element of the model. Elements with an element density above a threshold are treated as solid regions, and elements with an element density below a threshold are treated as hollow regions, resulting in the output shape of the topologically optimized variable region (step S204). This variable region is then combined with the invariant region to create the shape of the additively manufactured object.

[0039] If a phase optimization calculation is not performed in the variable domain design step (step S103), the solid and hollow regions of the variable domain can be determined by a second method using the cross-sectional area ratio.

[0040] In other words, the shape of the variable region is set to a predetermined shape having a specific hollow region pattern, such as a cylindrical or hexagonal prism shape with a symmetrical cross-section, and the size of the variable region is determined so that the ratio of the cross-sectional area occupied by the solid region to the cross-sectional area of ​​the product shape is a specified value. By making the hollow region pattern a shape with a symmetrical cross-section, isotropy can be obtained even when creating an additively manufactured body using thermoplastic resin, and deformation during the creation of the additively manufactured body can be suppressed. The specified value that defines the cross-sectional area ratio is the value β shown in the following equation (2). E inj =βE mex +(1-β)E opt ...(2) β: Specified value of the cross-sectional area ratio E inj Young's modulus of injection molded parts E mex : Young's modulus of the laminated structure E opt : Young's modulus of the variable region

[0041] According to the second method, in the first method, the specific restraint conditions, load conditions, and deformation conditions required as boundary conditions become unnecessary, and when the product shape is such that there is a region that is not affected by these conditions, or even when these conditions are absent, the variable region can be designed.

[0042] As described above, according to the present embodiment, the product shape is divided into an invariant region and a variable region, and the variable region is designed based on the rigidity of the injection molded body and the laminated structure. Therefore, a laminated structure having the same strength as a desired injection molded body can be designed. Hereinafter, examples according to the above-described embodiment will be described. The technology of the present disclosure is not limited to the following examples.

[0043] (Example 1) In Example 1, the variable region was designed by the first method using the phase optimization method.

[0044] In Example 1, a liquid crystalline resin (manufactured by Polyplastics Co., Ltd., Lapeiros (registered trademark) LCP A950) was used as the thermoplastic resin, and a strip-shaped test piece having a width of 10 mm, a thickness of 4 mm, and a length of 80 mm was injection molded. A three-point bending test conforming to ISO 178 was performed on this test piece. In this bending test, as shown in FIG. 4, the distance between the fixed jigs was set to 64 mm, a load cell was placed at the center of the test piece, the load cell was moved so that the strain rate was 1% / min, and the load was measured by a load sensor mounted on the test equipment. The amount of deformation at a load of 500 N was 3.25 mm.

[0045] Next, the product shape was divided into an invariant region and a variable region. Here, as shown in Figure 2, the invariant region was defined as a columnar body with a concave cross-section, and the variable region was defined as a rectangular parallelepiped surrounded on three sides by the invariant region. These invariant and variable regions were divided into cubic hexahedron linear elements to obtain finite element models for the invariant and variable regions, respectively.

[0046] Then, boundary conditions for topological optimization calculations were set in the finite element model. Specifically, as shown in Figure 5, full constraint conditions were applied at the constrained positions at both ends of the product shape, and a load of 500N was applied to the upper central part. Also, in equation (1) above, the Young's modulus E of the injection-molded body was... inj At 7400 MPa, the Young's modulus of the additively fabricated material is E mex The pressure was set to 23200 MPa and the correction factor f to 1.2, and the threshold α for the contribution rate was calculated to be 0.4. As the objective function, product compliance was set, and a phase optimization calculation was performed to minimize compliance.

[0047] In the topology optimization calculation, we used OptiStruct® from Altair Engineering to calculate the element density distribution of the finite element model. The results are shown in Figure 6. From these results, we used HyperView® from Altair Engineering to output the region with an element density of 0.46 or higher in STL (Standard Triangulated Language) format.

[0048] In this way, by using topological optimization calculations, we were able to remove the hollow region from the variable region and design a shape in which only the solid region remained. Then, by combining the designed variable region with the invariant region, we created the shape of the additively manufactured object. The resulting shape of the additively manufactured object is shown in Figure 7.

[0049] Next, in order to perform structural analysis calculations, the shape of the created additively manufactured body was divided into tetrahedral quadratic elements, and material properties were assigned assuming that the manufacturing path during additive manufacturing coincided with the longitudinal direction of the product shape. Specifically, the Young's modulus was set to 23200 MPa in the longitudinal direction of the product shape, and to 7850 MPa in the direction perpendicular to the longitudinal direction. Furthermore, a complete constraint condition was applied at the constraint position shown in Figure 5, and a load of 500 N was applied to the upper central part, after which a structural calculation was performed, resulting in a deformation of 3.23 mm. Figure 8 shows the deformation distribution of the above test piece molded by injection molding (Figure 8(a)) and the deformation distribution obtained by structural analysis calculation of the additively manufactured body (Figure 8(b)).

[0050] Thus, while the deformation of the injection-molded part was 3.23 mm, the deformation of the additively manufactured part predicted by structural analysis calculations was 3.25 mm, resulting in an error of 0.6%. Therefore, the rigidity and strength of the additively manufactured part designed using the phase optimization method are sufficiently close to those of the injection-molded part, and it was possible to design an additively manufactured part with equivalent strength to the injection-molded part with good accuracy.

[0051] (Example 2) In Example 2, the variable region was designed by a second method, which involved adjusting the cross-sectional area ratio to a specified value.

[0052] In Example 2, a liquid crystalline resin (Laperos® LCP A950, manufactured by Polyplastics Co., Ltd.) was used as the thermoplastic resin, and test specimens conforming to ISO 527 were molded by injection molding. A tensile test was performed on these test specimens in accordance with ISO 527. As a result, the Young's modulus was 7400 MPa.

[0053] Next, similar to Example 1, the rectangular product shape, with a width of 10 mm, a thickness of 4 mm, and a length of 80 mm, was divided into an invariant region and a variable region. That is, similar to Example 1, the invariant region was made into a columnar body with a concave cross-section, and the variable region was made into a rectangular parallelepiped surrounded on three sides by the invariant region (Figure 2). These invariant and variable regions were divided into cubic hexahedral linear elements to obtain finite element models for the invariant and variable regions, respectively.

[0054] In Example 2, the shape of the variable region was predetermined to have a hexagonal prism-shaped hollow region pattern as shown in Figure 9. The hexagon in the cross-section of the hollow region pattern is sized to be inscribed in a circle with a diameter of 1 mm, and the thickness of the solid region defining the hollow region pattern is 0.2 mm.

[0055] Then, boundary conditions for structural analysis calculations were set for the finite element model. Specifically, as shown in Figure 10, one end in the longitudinal direction was fully constrained, and a forced displacement of 8 mm was applied to the surface of the other end in the longitudinal direction. Under these boundary conditions, the total rebound force of the constrained portion was calculated by structural analysis calculation, and the value obtained by dividing the total rebound force by the cross-sectional area was 3500 MPa. Also, in equation (2) above, the Young's modulus E of the injection-molded body. inj At 7400 MPa, the Young's modulus of the additively fabricated material is E mex The pressure was set to 23200 MPa, and the Young's modulus Eopt in the variable region was set to 3500 MPa as calculated above. The specified value β for the cross-sectional area ratio was calculated to be 0.20.

[0056] Then, by adjusting the size of the variable region with a hexagonal prism-shaped hollow region pattern so that the cross-sectional area ratio was 0.20, the variable region became 8.8 mm wide and 3.6 mm thick.

[0057] In this way, by adjusting the size of the variable region so that the cross-sectional area ratio becomes a specified value, it was possible to design a variable region with a predetermined hollow region pattern. Then, by combining the designed variable region with the invariant region, the shape of the additively manufactured object was created. Figure 11 shows the shape of the additively manufactured object. Figure 11(a) is a perspective view showing the shape of the additively manufactured object, and Figure 11(b) is a cross-section of line II in Figure 11(a). As shown in these figures, the variable region with a hexagonal prism-shaped hollow region pattern is a rectangular parallelepiped shape with a width of 8.8 mm and a thickness of 3.6 mm, surrounded on three sides by the invariant region.

[0058] Next, in order to perform a structural analysis calculation similar to that in Example 1, the shape of the created additively manufactured body was divided into tetrahedral quadratic elements, and material properties were assigned assuming that the manufacturing path during additive manufacturing coincided with the longitudinal direction of the product shape. Specifically, the Young's modulus was set to 23200 MPa with respect to the longitudinal direction of the product shape. Furthermore, when the structural calculation was performed with boundary conditions similar to those shown in Figure 10, a Young's modulus of 7470 MPa was obtained from the resulting repulsive force. Figure 12 shows the deformation distribution of the above test piece molded by injection molding (Figure 12(a)) and the deformation distribution obtained by the structural analysis calculation of the additively manufactured body (Figure 12(b)).

[0059] Thus, while the Young's modulus of the test specimen molded by injection molding was 7400 MPa, the Young's modulus of the additively manufactured body predicted by structural analysis calculations was 7470 MPa, with an error of 0.95%. Therefore, the rigidity and strength of the additively manufactured body designed using the cross-sectional area ratio are sufficiently close to those of the injection-molded body, and it was possible to design an additively manufactured body with strength equivalent to that of an injection-molded body with good accuracy.

[0060] The shape design method for an anisotropic additive manufacturing body according to the above embodiment can be executed by an information processing device. Figure 13 is a block diagram showing an example of the hardware configuration of an information processing device 100 that executes the shape design method for an anisotropic additive manufacturing body. As shown in Figure 13, the information processing device 100 has a processor 101, a main memory 102, an auxiliary memory 103, an I / O (Input / Output) interface 104, and a network interface (hereinafter abbreviated as "NW interface") 105.

[0061] The processor 101 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or a DSP (Digital Signal Processor), and provides overall control of the information processing device 100, as well as executing various arithmetic operations.

[0062] The main memory 102 includes, for example, RAM (Random Access Memory) or ROM (Read Only Memory) and stores information used for arithmetic processing performed by the processor 101.

[0063] The auxiliary storage device 103 includes, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various programs and data.

[0064] The I / O interface 104 is an interface that allows the user to input information or output information to the user. The I / O interface 104 may include, for example, a keyboard, display, touch panel, microphone, or speaker.

[0065] The NW interface 105 is an interface that connects to a network via wired or wireless connection.

[0066] The information processing device 100 receives input such as the shape and anisotropic physical property values ​​of an anisotropic additive manufacturing body via the I / O interface 104 and the NW interface 105. The processor 101 then uses the main memory 102 to execute a program stored in the auxiliary memory 103 to create a structural analysis model of the anisotropic additive manufacturing body, and performs structural analysis using the structural analysis model.

[0067] Furthermore, the above shape design method can also be described as a computer-executable program. In this case, this program can be stored in a computer-readable and non-transitory recording medium and installed on the computer. Examples of such recording media include portable recording media such as CD-ROMs, DVD discs, and USB memory, as well as semiconductor memory such as flash memory.

[0068] In relation to the technology described above, the following is further disclosed:

[0069] [1] A step of dividing the shape of an anisotropic additively manufactured object into an invariant region in which no change in shape is permitted and a variable region in which change in shape is permitted, The steps include designing the variable region obtained by division based on the rigidity of an injection-molded body having the same shape as the anisotropic additively fabricated body, The steps include: performing structural analysis calculations using a structural analysis model of an additively manufactured body obtained by combining a designed variable region and the invariant region; A step of determining whether the rigidity and strength of the additively fabricated body obtained by structural analysis calculations are within an acceptable range, A shape design method having the following characteristics.

[0070] [2] The anisotropic additive body is fabricated by material extrusion (MEX). The shape design method described in [1] above.

[0071] [3] The design step is: The solid and hollow regions of the variable region are determined by performing a phase optimization calculation. The shape design method described in [1] or [2] above.

[0072] [4] The design step is: The topological optimization calculation is performed under the condition that the contribution rate, which represents the degree to which the deformation of elements obtained by dividing the shape of the anisotropic additive manufacturing structure into minute regions contributes to the deformation of the overall shape of the anisotropic additive manufacturing structure, satisfies the threshold α of the contribution rate shown in equation (1) above. The shape design method described in [3] above.

[0073] [5] The design step is: The size of the variable region is determined such that the ratio of the cross-sectional area of ​​the solid portion to the hollow portion of the anisotropic additive body shape is a predetermined value. The shape design method described in [1] or [2] above.

[0074] [6] The design step is: The size of the variable region having a predetermined hollow region pattern is determined such that the cross-sectional area ratio is the specified value β shown in equation (2) above. The shape design method described in [5] above.

[0075] [7] Computers, The steps include dividing the shape of an anisotropic additively manufactured object into an invariant region where shape modification is not permitted and a variable region where shape modification is permitted, The steps include designing the variable region obtained by division based on the rigidity of an injection-molded body having the same shape as the anisotropic additively fabricated body, The steps include: performing structural analysis calculations using a structural analysis model of an additively manufactured body obtained by combining a designed variable region and the invariant region; A step of determining whether the rigidity and strength of the additively fabricated body obtained by structural analysis calculations are within an acceptable range, A shape design program that executes this process. [Explanation of Symbols]

[0076] 101 Processors 102 Main storage 103 Auxiliary storage device 104 I / O Interfaces 105 NW Interface

Claims

1. The steps include dividing the shape of an anisotropic additively manufactured object into an invariant region where shape modification is not permitted and a variable region where shape modification is permitted, The steps include designing the variable region obtained by division based on the rigidity of an injection-molded body having the same shape as the anisotropic additively fabricated body, The steps include: performing structural analysis calculations using a structural analysis model of an additively manufactured body obtained by combining a designed variable region and the invariant region; A step of determining whether the rigidity and strength of the additively fabricated body obtained by structural analysis calculations are within an acceptable range, A shape design method having the following characteristics.

2. The aforementioned anisotropic additively fabricated body is manufactured by material extrusion (MEX). The shape design method according to claim 1.

3. The aforementioned design step is, The solid and hollow regions of the variable region are determined by performing a phase optimization calculation. The shape design method according to claim 1.

4. The aforementioned design step is, The topological optimization calculation is performed under the condition that the contribution rate, which represents the degree to which the deformation of elements obtained by dividing the shape of the anisotropic additive manufacturing structure into minute regions contributes to the deformation of the overall shape of the anisotropic additive manufacturing structure, satisfies the threshold α of the contribution rate shown in the following equation (1). The shape design method according to claim 3. [Math 1] α: Threshold for contribution rate E inj Young's modulus of injection molded parts E mex : Young's modulus of additively manufactured objects f: Correction factor

5. The aforementioned design step is, The size of the variable region is determined such that the ratio of the cross-sectional area of ​​the solid portion to the hollow portion of the anisotropic additive body shape is a predetermined value. The shape design method according to claim 1.

6. The aforementioned design step is, The size of the variable region having a predetermined hollow region pattern is determined such that the cross-sectional area ratio is the specified value β shown in the following equation (2). The shape design method according to claim 5. E inj =βE mex + (1-β)E opt ・・・(2) β: Specified value of the cross-sectional area ratio E inj Young's modulus of injection molded parts E mex : Young's modulus of additively manufactured objects E opt : Young's modulus of the variable region

7. On the computer, The steps include dividing the shape of an anisotropic additively manufactured object into an invariant region where shape modification is not permitted and a variable region where shape modification is permitted, The steps include designing the variable region obtained by division based on the rigidity of an injection-molded body having the same shape as the anisotropic additively fabricated body, The steps include: performing structural analysis calculations using a structural analysis model of an additively manufactured body obtained by combining a designed variable region and the invariant region; A step of determining whether the rigidity and strength of the additively fabricated body obtained by structural analysis calculations are within an acceptable range, A shape design program that executes this process.

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