Method and computer program product for adapting a model of a three-dimensional object by replacing grid geometry with polygonal geometry

Abstract

The invention relates to a method for adapting a model of a three-dimensional object (2). A starting model of the object (2) is optimized into the form of a shell model (1) using an optimization process. A base-surface-free rib grid model (5) is extracted from the shell model (1) and is transformed into a rib polygonal model (6). The rib polygonal model (6) is used to adapt the starting model of the object (2) in that the ribs (2.2) of the starting model are replaced with the rib polygonal model (6).

Description

[0001] Method and computer program product for adapting a model of a three-dimensional object by replacing mesh geometry with polygon geometry

[0002] The invention relates to a method for adapting a three-dimensional object, in particular a component to be manufactured, a computer program product and an object manufactured according to the method.

[0003] For example, DE 102021 003 565 A1 discloses methods in which an optimization result of a component, in particular an optimization result of a topology of the component, is used to construct a CAD geometry of the component based on the optimization result. The component, in particular the CAD geometry of the component, is manually created using geometries of design elements in such a way that the optimization result of the component and the CAD geometry of the component are almost identical. The manual creation of the CAD geometry of the component is necessary because the optimization result of the component only contains visualizable data and no geometrically usable data. The time required to manually create the CAD geometry of a sub-area of ​​a simple component is at least a few minutes, although the time required for more complex components increases rapidly with increasing complexity.In one of the known methods, the CAD geometry of the component is created using a CAD system - in particular Siemens NX.

[0004] US 2022 / 0284153 A1 discloses another method in which a computer system accesses models of an object, in particular geometries, in connection with an optimization process, in particular a topology optimization process. These geometries comprise an initial geometry representing a design space to which the topology optimization process is applied, and an optimized geometry representing a result of the topology optimization process performed on the initial geometry. The method also includes generating a final geometry from the topology-optimized geometry. This is done by adapting the topology-optimized geometry to the initial geometry at locations that correspond to fixed regions of the initial geometry. In addition, the topology-optimized geometry is smoothed at locations that do not correspond to fixed regions of the initial geometry.

[0005] The invention is based on the object of providing an improved method for adapting a three-dimensional object, a computer program product and an object produced according to the method.

[0006] The first-mentioned object is achieved according to the invention by a method for adapting a three-dimensional object having the features of claim 1. The second-mentioned object is achieved according to the invention by a computer program product having the features of claim 9. The third-mentioned object is achieved according to the invention by the features of claim 10.

[0007] Advantageous further developments of the invention are the subject of the subclaims.

[0008] In a method according to the invention for adapting a three-dimensional object, an initial model of the object is used, which contains a base surface and associated ribs. An optimization process is used to generate an optimized model of the object in the form of a shell model from the initial model of the object. A base-free rib mesh model is extracted from this shell model and transformed into a rib polygon model. The generated rib polygon model is used to adapt the object by replacing the ribs from the initial model of the object with the rib polygon model.

[0009] The advantages achieved with the invention are, in particular, that optimized ribs of an object, for example, created from finite element optimizations in a computer-aided engineering (CAE) tool, can be precisely transferred to a computer-aided design (CAD) tool and replace the non-optimized ribs of the object's initial model in the CAD tool, thereby adapting the object. Furthermore, the transferred optimized ribs can be further modified by an engineer in the CAD tool, if necessary, in a more detailed manner, since the representation of the ribs is more detailed.

[0010] In other words, the method automatically transfers the optimized ribs from the CAE tool to the CAD tool, avoiding the traditional tedious, time-consuming, and inaccurate process of parametrically redesigning optimized ribs for further transfer to the CAD tool.

[0011] This makes it possible to easily and quickly construct objects such as vehicle components with improved functionality, reduced weight and / or optimized topology, which is advantageous for manufacturing and component production.

[0012] The three-dimensional object can, for example, be a component to be manufactured, for example a plastic component, a cast component, a forged component, an extrusion component, a 3D printed component, an injection-molded component, a deep-drawn component or the like.

[0013] Such structural objects or components can be freely designed in terms of shape, material and / or thickness distribution with few manufacturing restrictions.

[0014] A rib mesh model is considered part of the optimized shell model. One advantage of optimizing the ribs together with the entire object is the synergistic effect of this optimization. The ribs are intended to ensure stability and load distribution on the object. Therefore, the rib parameters should be optimized together with the entire object.

[0015] In one possible embodiment, information about at least one rib parameter is transferred to a rib mesh cell of the extracted rib mesh model. A rib parameter is understood to be, for example, topological and / or physical object parameters, such as thickness information, material information, or the like. A rib mesh cell is a cell of the rib mesh model that is part of the shell model of the object. A rib mesh cell can, for example, comprise one or more parameter values. The parameter values ​​can, for example, be stored in the nodes of the rib mesh cell. In this way, the information resulting from the optimization process can be compactly stored in the rib mesh model. The granularity of the mesh can vary depending on the desired precision of the optimization process. The granularity can be homogeneous or non-homogeneous.For example, the parts of the object or ribs that are of greater interest for optimization can be associated with a finer granularity.

[0016] In another possible embodiment, a rib segment is generated based on at least one rib mesh cell and associated information about at least one rib parameter. The size of the rib segment corresponds to at least one rib parameter. Depending on how precisely the information from the optimized rib mesh model is to be transferred for adapting the object, the rib segment is built on one or more rib mesh cells. The fewer rib mesh cells used for the rib segment, the more precisely the results of the optimization process are reflected in the rib polygon model. However, the CAD tool only supports the transfer of a limited amount of information. Therefore, a compromise should be found between precision and limiting the transfer of information.

[0017] In another possible embodiment, the respective rib segment is generated using individual polygons. Individual polygons provide a practical and compact way to transfer information about optimized parameters to, for example, a CAD tool for adjusting the object.

[0018] In another possible embodiment, the rib segment is generated from a top edge of the rib mesh cell to a base side that flows into the base surface. In this way, it is possible to incorporate information about the optimized parameters, such as the thickness of the rib, into the rib mesh model. First, a top side of the rib segment is formed, and then a finished rib segment is obtained by extruding the top side to the base surface. This operation is resource-efficient and useful for production processes such as casting. During casting, it is possible to vary the thickness along the rib, but the vertical direction of the rib, which is perpendicular to the main surface of the object, is limited in its thickness change. After casting, however, it should be possible to remove the object from the mold.For production processes such as 3D printing, where this restriction does not apply, the rib polygon model can include polygon segments not only along the rib, but also along multiple polygon segments perpendicular to the main surface of the object, to represent thickness optimization in this direction. The information for constructing a rib polygon model for both alternatives is contained in the rib mesh model. This makes it possible to produce objects with optimized ribs, resulting in optimal object construction and material savings.

[0019] In another possible embodiment, a side surface of the rib segment is created using an associated draft angle. In casting, for example, liquid material is poured into a mold to produce an object. The draft angle is the angle between the mold and the surface of the object that is required to remove the object from the mold. A draft angle that is too small can prevent the object from being released from the mold, while a draft angle that is too large can impair the object's appearance. Therefore, it is important to carefully consider the draft angle when producing objects by casting. With a given draft angle, it is still possible to produce ribs, for example, with inhomogeneous thicknesses determined by the different sizes of the head polygons of the rib segments.This allows the ribs to be designed to meet the requirements of the part without having to adjust the draft angle. This is particularly useful when manufacturing parts with complex geometries where a uniform rib thickness is not sufficient.

[0020] In another possible embodiment, the rib polygon model is formed from several generated rib segments. The rib polygon model has a practical and compact form for transferring information on optimized parameters to, for example, a CAD tool for adapting the object.

[0021] In another possible embodiment, a final object model is created by combining the generated rib polygon model with the base area of ​​the original model. In other words, a final object model can be created using the model tool based on the generated rib polygon model and a geometric CAD model of the object. Using the model tool, in particular a computer-aided design system, the optimized rib polygons can, for example, be combined, in particular merged, with the geometric base area of ​​the geometric CAD model of the object. In this way, the object is adapted so that it has ribs with optimal geometry and / or topology.

[0022] The improved topology and geometry of the ribs are of great importance for technical purposes. Optimizing the rib geometry increases the stiffness of the object, resulting in better mechanical stability. Furthermore, the optimized rib geometry can also contribute to reducing the weight of the object.

[0023] The computer program product according to the invention comprises machine-readable instructions on the basis of which the method described above is carried out when the computer program product runs on a computing device, in particular a modeling tool, for example a design tool and / or a construction tool.

[0024] The object according to the invention comprises a structure with optimized ribs, which was manufactured by the method described above.

[0025] Embodiments of the invention are explained in more detail below with reference to a drawing.

[0026] Showing:

[0027] Fig. 1 schematically shows an optimized CAE model of a three-dimensional object with a rib mesh model,

[0028] Fig. 2 shows a schematic example of a base-free rib mesh model extracted from the CAE model,

[0029] Fig. 3 schematically shows a rib polygon model and the creation of a rib polygon model based on the rib mesh cells of a generated rib mesh model,

[0030] Fig. 4 shows a schematic example of the creation of a rib segment, Fig. 5 shows a schematic example of a rib polygon model transformed from the rib mesh model, and

[0031] Fig. 6 schematically adapted final object model with replaced ribs by the generated rib polygon model.

[0032] Corresponding parts are provided with the same reference numerals in all figures.

[0033] Figure 1 schematically shows an optimized shell model 1, in particular a CAE model, of a three-dimensional object 2. The shell model 1 is hereinafter referred to as CAE model 1.

[0034] The object 2 can, in particular, be a vehicle component, such as a sheet metal component or body component. The object 2 can, in particular, be a component to be manufactured, for example, a plastic component, a cast component, a forged component, an extruded component, a 3D-printed component, an injection-molded component, a deep-drawn component, or the like.

[0035] Such structural objects 2 or components can be freely designed, designed and manufactured in terms of shape, material and / or thickness distribution.

[0036] The object 2 is a three-dimensional component or a three-dimensional body that can be described by its base surface 2.1 and / or ribs 2.2. The base surface 2.1 can be formed or composed of flat and / or curved surface pieces or surface sections and can be provided with elevations, for example in the form of ribs 2.2, brackets, pins, cones, or the like. For clarity, the invention will hereinafter refer to ribs 2.2. However, the ribs 2.2 can be any other functional subunit connected to the object 2.

[0037] The CAE model 1 of object 2 corresponds to a geometric initial model with a homogeneous thickness distribution (hereinafter referred to as CAE model 1). The CAD model is a raw geometric representation of object 2. The CAD model comprises model structure data or CAD geometry data and can, for example, be imported into a CAE tool in digital form. The exported CAD model 4 is optimized by simulation, for example using a model tool 3, in particular a CAE tool, and represented in the form of the shell model 1, in particular a finite element mesh. The result of this process is the optimized model of object 2. This process is carried out with the entire initial model of object 2, including the base area 2.1 and the ribs 2.2.

[0038] The modeling tool 3 is, for example, a computer or a processing unit on which a corresponding computer program product, such as a graphics file and / or a computer graphics program, can be loaded and executed. In particular, the modeling tool 3 is a design and / or construction tool.

[0039] A mesh 1.1 (also called a finite element mesh) of the CAE model 1 comprises a plurality of mesh cells 1.2 and a plurality of mesh lines 1.3. The mesh 1.1 is designed, for example, as a structured quadrilateral mesh. Alternatively, the mesh 1.1 can also be a triangular mesh or the like. Each mesh cell 1.2 of the mesh 1.1 is associated with a scalar value of a physical and / or topological parameter of the optimized CAE model 1. The scalar values ​​can, for example, represent information about the thickness distribution 2.3 of the object 2. The CAE model 1 shown is, in particular, a thickness-optimized CAE model 1.

[0040] In some cases, after optimization through simulation, some scalar values ​​of physical parameters, such as thickness, may be discontinuous. This means that there are abrupt changes in thickness between neighboring cells of the mesh. To resolve this, object 2 is optionally checked for such abrupt thickness changes and / or discontinuities during the creation of the thickness-optimized CAE model 1. These abrupt thickness changes can be smoothed using model tool 3. The optimization step (also called smoothing step) is not shown.

[0041] The invention is described below by way of example for the optimization of the ribs 2.2 with a changing, in particular variable or inhomogeneous, rib shape, in particular a variable height and / or a variable thickness of the ribs 2.2. For example, a base-free rib mesh model 5 can be extracted or isolated from the thickness-optimized CAE model 1 using the model tool 3, shown in Figure 2.

[0042] The generated rib mesh model 5 can be used to adapt the object 2, as described in more detail below.

[0043] Figure 2 shows a schematic example of a base-free rib mesh model extracted from CAE Model 1.

[0044] The extracted rib mesh model 5 does not include the base area 2.1 of the object 2, but only the optimized shell model of the ribs 2.2.

[0045] The rib mesh model 5 is a shell model, specifically a finite element model, and is generated by a multitude of rib mesh lines 5.4. The rib mesh model 5 is created by isolating the ribs 2.2 from the base surface 2.1 of the optimized CAE model of object 2. If the optimized CAE model of object 2 was smoothed in the previous step to avoid abrupt parameter changes and / or discontinuities, the rib mesh model 5 already exists in a smoothed version. Alternatively, smoothing can also be performed only for the rib mesh model 5 after isolating the ribs 2.2 from the base surface 2.1 of the optimized CAE model of object 2.

[0046] The rib mesh 5.1 is designed, for example, as a structured quadrilateral mesh. Alternatively, the rib mesh 5.1 can also be a triangular mesh or the like.

[0047] Rib mesh cell 5.3 of the extracted rib mesh model 5 transmits information about at least one rib parameter. The parameter values ​​can, for example, be stored in the nodes of rib mesh cell 5.3. For example, rib mesh cell 5.3 transmits scalar values ​​for the thickness and / or thickness distribution 2.3 of the ribs 2.2 at a specific rib mesh cell. In addition to thickness, rib mesh cell 5.3 can also transmit other parameters, such as material composition, material properties, or similar. Rib mesh model 5 is further used to create a rib polygon model 6, which is then transferred to the CAD tool to replace the ribs 2.2 of the original CAD model 4.

[0048] Figure 3 schematically shows a rib polygon model 6 and the creation of a rib polygon model 6 based on the rib mesh cells 5.3 of a generated rib mesh model 5.

[0049] Creation refers to the generation of rib polygon models 6 based on a rib mesh model 5. This is done using information about the thickness transmitted in the rib mesh cells 5.3.

[0050] To create the rib polygon model 6 from the extracted rib mesh model 5, thickness information, for example, a rib thickness 5.6, is first extracted for the respective rib 2.2 from the scalar values ​​of the rib mesh cells 5.3 of the rib mesh model 5 at several top edge points 5.5.1 along a top edge 5.5 of the rib mesh model 5. The top edge points 5.5.1 are the nodes of the corresponding rib mesh cells 5.3.

[0051] The rib thickness 5.6 can, for example, be in the millimeter or centimeter range. The corresponding rib thickness 5.6 is determined for each top edge point 5.5.1.

[0052] Based on these rib thicknesses 5.6 along the upper edge 5.5 of the rib mesh cell 5.3, a rib segment 6.1 is created.

[0053] Figure 4 schematically shows an example of creating a rib segment. A head polygon 6.2 of rib segment 6.1, generated based on the rib thickness 5.6 at the top edge 5.5, represents the upper end face or surface of rib 2.2. Side faces 6.3 (also called flanks) are then created by extruding or forming them with a specified draft angle 6.4 for their face angle or flank angle. The draft angle 6.4 leads to a base face 6.5 (also called the bottom face), which represents the base face 6.6 of rib segment 6.1 of the rib polygon model 6. This base face 6.5 is closed, for example, as a surface. As described later in the text, the base face 6.6 is merged with the base face 2.1 of object 2 to adjust object 2.

[0054] This simplified rib segment 6.1, consisting of the head polygon 6.2, the two side faces 6.3, and the base face 6.5, features a minimal number of individual polygons. This allows for quick and efficient geometry adaptation when changes are made to the final object model 8 in the CAD tool, for example, rib parameters such as rib height, rib thickness 5.6, rib length, or similar.

[0055] With reference to Figure 3, the majority of the rib segments 6.1 are merged to form a rib polygon model 6, as shown in Figure 5. Optionally, the side surfaces 6.3 can be smoothed at the joints to create continuous transitions between the rib segments 6.1.

[0056] In another embodiment, the production process is carried out, for example, by 3D printing, such as laser powder deposition welding. During 3D printing, the side surfaces 6.3 can be formed based on the thickness information transmitted in the rib mesh cells 5.3. In other words, the thickness of the rib polygon model 6.1 can vary not only along the rib, but also transversely or vertically to it.

[0057] In another embodiment, the rib segment 6.1 is based on two, three, or more upper rib mesh cells 5.3. In other words, the thickness information is taken from every second, third, or nth rib mesh cell 5.3. The rib segments 6.1 approximate the optimized thickness contained in the rib mesh model 5. The fewer rib segments 6.1 the rib polygon model 6 has, the less precise the optimization results achieved by CAE modeling, which are represented by the rib polygon model 6. The results contained in the rib mesh model 5 are transferred to the CAD tool to create the final object model 8. However, the CAD tool only supports the transfer of a limited amount of information, so a compromise should be achieved between precision and limiting the information transfer.Figure 5 schematically shows an example of a rib polygon model 6 that was transformed from the rib mesh model 5. The rib polygon model 6 is formed by several combined rib segments 6.1 in order to further process it and merge it with the geometric CAD model 4 with homogeneous thickness distribution to create a final object model 8 of the object 2 with inhomogeneous thickness distribution of the ribs, as shown in Figure 6.

[0058] Figure 6 shows a schematic example of an adapted final object model 8 with replaced ribs by the generated rib polygon model 6. The final object model 8 is generated using the model tool 3 as a hybrid model from the optimized rib polygon model 6 with inhomogeneous thickness distribution and the geometric CAD model 4 with homogeneous thickness distribution.

[0059] Using the computer-aided modeling tool 3, the rib polygon model and the base surface 2.1 of the CAD model 4 can be combined, in particular merged. In this case, corresponding interfaces 7 can optionally be smoothed at the intersection edges of the rib polygon model 6 and at the intersection edges of the base surface 2.1. For this purpose, a known standard or manipulation method of the modeling tool 3, which is designed as a CAD system, can be employed or used, such as Boolean operations such as Boolean additions.

[0060] The final object model 8 comprises, for example, first regions 8.1 with a homogeneous thickness distribution, which are formed unchanged from the CAD model 4. The final hybrid or object model 8 comprises second regions 8.2 with an inhomogeneous thickness distribution, which are formed from the rib polygon model 6, which in turn was formed from the rib mesh model 5.

[0061] For this purpose, for example, using the model tool 3, data from the CAD model 4 for the first areas 8.1 and data from the CAE rib polygon model 6 for the second areas 8.2 can be imported or loaded and networked, in particular, knotted. Optionally, the respective rib segments 6.1 can be further modified, as described above, for example, by changing the head polygons 6.2, the side surfaces 6.3, and / or the base sides 6.5. The final object model 8 is a CAD geometry that additionally includes the geometric CAD model 4 and the CAE rib polygon model 6 in sections.

[0062] In other words: In the final step of the construction, the first areas 8.1 of the parametric CAD model 4 and the second areas 8.2 of the CAE rib polygon model 6 can be linked together and the final object model 8 can be created with first areas 8.1 with homogeneous thickness distribution and with second areas 8.2 with inhomogeneous thickness distribution.

[0063] Interfaces 7 or transitions between areas 8.1 and 8.2 can be smoothed using trimming operations. These trimming operations then generate the final object model 8.

[0064] Advantageously, the rib polygon model 6 of the object 2, in particular of the component to be manufactured, has geometrically usable data, so that the creation of the CAD geometry is possible in a simple and fast manner and in particular in an automated manner.

Claims

Patent claims 1. A method for generating a CAD model, comprising CAD geometry data of a three-dimensional object (2), wherein an initial model of the object (2) contains a base area (2.1) and ribs (2.2) connected thereto, an optimized model of the object (2) in the form of a shell model (1) is generated from the initial model of the object (2) by means of an optimization process, a base area-free rib mesh model (5) is extracted from the shell model (1) of the object (2), the generated rib mesh model (5) is transformed into a rib polygon model (6), the rib polygon model (6) is used to adapt the object (2) by replacing the ribs (2.2) from the initial model of the object (2) with the rib polygon model (6), wherein it is further provided that information about at least one rib parameter is transferred to a rib mesh cell (5.3) of the extracted rib mesh model (5), and a Rib segment (6.1) based on at least one rib mesh cell (5.3) and associated information about at least one rib parameter is generated, wherein the size of the rib segment (6.1) corresponds to at least one rib parameter.

2. Method according to claim 1, characterized in that the respective rib segment (6.1) is generated using individual polygons.

3. Method according to claim 1 or 2, characterized in that the rib segment (6.1) is produced from an upper edge (5.5) of the rib network cell (5.3) towards a base side (6.5) which opens into the base area (6.6).

4. Method according to one of claims 1 to 3, characterized in that a side surface (6.3) of the rib segment (6.1) is produced with the aid of an associated demolding angle (6.4).

5. Method according to one of claims 1 to 4, characterized in that the rib polygon model (6) is formed by several generated rib segments (6.1).

6. Method according to claim 5, characterized in that a final object model (8) is created by merging the generated rib polygon model (6) with the base area (2.1) of the initial model.

7. A computer program product comprising machine-readable instructions on the basis of which a method according to any one of the preceding claims is carried out when the computer program product is run on a computing device.

8. A component, characterized by a geometry corresponding to a three-dimensional object (2) which is impressed on the component by its manufacture, wherein the geometry of the three-dimensional object (2) is described by CAD geometry data which are contained in a CAD model which was generated according to a method according to one of claims 1 to 6.

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