Method for generating full-laying path of three-dimensional model of dieless mirror image filament laying

Abstract

A mold-free mirror image three-dimensional model full laying path generation method, based on model characteristics and laying requirements, determines the three-dimensional model laying reference boundary surface and generates the neutral surface, and takes the generated neutral surface laying path as the basis, through the mirror image offset and filtering processing, the three-dimensional model full laying path is generated. The invention generates the laying path of the three-dimensional model by the equidistant mirror image offset and filtering processing of the neutral surface laying path, avoids the inefficient and tedious steps of generating the path after slicing in the traditional method, and realizes the optimization and automatic generation of the three-dimensional model full laying path.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of automatic fiber placement manufacturing, and particularly relates to a mold-free mirror image fiber placement three-dimensional model full placement path generation method. BACKGROUND

[0002] The mold-free mirror image fiber placement process involves cooperative motion control of multiple fiber placement ends and cooperative action control of multiple fiber placement end function mechanisms, and efficient automatic control of the mold-free mirror image fiber placement equipment depends on a high-precision and efficient fiber placement path generation method. SUMMARY

[0003] The application provides a mold-free mirror image fiber placement three-dimensional model full placement path generation method, which avoids the inefficient and cumbersome steps of generating a path after slicing in the traditional method, and realizes automatic generation of a three-dimensional model full placement path.

[0004] The application is implemented by the following technical scheme:

[0005] The application relates to a mold-free mirror image fiber placement three-dimensional model full placement path generation method, which generates a three-dimensional model full placement path by determining a reference surface for three-dimensional model fiber placement based on model characteristics and fiber placement requirements, generating a neutral surface, taking the generated neutral surface fiber placement path as a basis, and performing mirror image offsetting and filtering processing in cycles.

[0006] The neutral surface is generated by determining a three-dimensional model fiber placement reference boundary surface based on a fiber placement direction in an imported three-dimensional model, converting the fiber placement reference boundary surface solid model into a triangular mesh surface model, extracting triangular mesh information of the fiber placement reference boundary surface, and generating a neutral surface equidistant to the two fiber placement reference boundary surfaces according to mesh node numbers, node coordinates, mesh element numbers and mesh element normal vectors.

[0007] The neutral surface fiber placement path is generated by generating neutral surface triangular mesh element information, generating a neutral surface fiber placement path by using an equidistant plane intersection method, giving a fiber placement reference axis, a fiber placement angle and a fiber placement width, generating an equidistant plane based on the parameters, calculating the intersection points of the equidistant plane and each triangular mesh element of the neutral surface, and performing sorting and path smoothing processing on the intersection points to generate a path on the neutral surface.

[0008] The mirror image biasing biases the path points on the neutral plane along the normal positive direction and the normal negative direction of the triangular unit where the path points are located, according to the preset layer thickness.

[0009] The filtering processing judges the relative position between the generated mirror image fiber laying path points and the fiber laying reference plane, filters the generated mirror image fiber laying path, removes the path points located outside the two fiber laying reference boundary surfaces, and only keeps the path points inside the two fiber laying reference boundary surfaces.

[0010] The cycle processing gradually increases the distance of the mirror image biasing according to the layer thickness, generates new mirror image fiber laying paths after filtering, and is performed until all the generated mirror image fiber laying paths are located outside the two fiber laying reference boundary surfaces, at which time all the generated mirror image fiber laying paths can accurately fill the three-dimensional model.

[0011] The present application relates to a moldless mirror image fiber laying three-dimensional model full laying path generation system for realizing the above method, comprising a three-dimensional model processing module, a neutral plane generation module, a neutral plane path generation module, a mirror image path generation and filtering module, and a three-dimensional model full laying path generation module, wherein: the three-dimensional model processing module imports and pre-processes the three-dimensional model of the manufacturing component; the neutral plane generation module determines the fiber laying reference boundary surface based on the characteristics of the three-dimensional model, converts the surface entity model into a triangular mesh model, extracts the triangular mesh information of the reference surface, generates a neutral plane equidistant to the two fiber laying reference boundary surfaces based on the mesh information; the neutral plane path generation module generates the neutral plane fiber laying path by using the equidistant plane intersection method based on the generated neutral plane triangular mesh unit information, generates the equidistant plane based on the control parameters and calculates the intersection points of the equidistant plane and each triangular mesh unit of the neutral plane, sorts and smoothes the intersection points to generate the path on the neutral plane; the mirror image path generation and filtering module biases the path points on the neutral plane along the normal positive direction and the normal negative direction of the triangular unit where the path points are located, according to the preset layer thickness, judges the relative position between the generated mirror image fiber laying path points and the fiber laying reference plane, filters the generated mirror image fiber laying path, removes the path points located outside the two fiber laying reference boundary surfaces, and only keeps the path points inside the two fiber laying reference boundary surfaces; the three-dimensional model full laying path generation module gradually increases the biasing distance according to the preset layer thickness, cyclically generates the mirror image path and performs filtering until all the generated mirror image paths are located outside the three-dimensional model, thereby generating the full laying path of the three-dimensional model.

[0012] The pre-processing includes: importing, checking, repairing, translating, rotating, enlarging, reducing, view switching, color rendering, determining the fiber laying reference boundary surface, extracting the triangular mesh information of the fiber laying reference boundary surface, and storing the triangular mesh information of the fiber laying reference boundary surface.

[0013] The triangular mesh information includes: triangular mesh node number, node coordinates, mesh element number, mesh element face normal vector.

[0014] The control parameters include: fiber laying reference axis, fiber laying angle, fiber laying width, shortest fiber laying path length, minimum fiber laying path curvature radius.

[0015] Technical effects

[0016] The present application is aimed at the characteristics of mirror image fiber laying process that two sides are symmetrically laid at the same time, and in order to solve the problem of full laying path optimization generation of a three-dimensional model with a non-parametric curved boundary, a path generation strategy is proposed, which firstly generates a neutral surface based on the model fiber laying reference boundary surface information, then generates a fiber laying path on the neutral surface, then offsets the neutral surface path to the two sides of the fiber laying reference boundary surface by mirror image, and finally filters the offset mirror image path until the full laying path of the three-dimensional model is generated. The above three-dimensional model full laying path generation method and strategy for mirror image fiber laying process have never been disclosed. Compared with the prior art that generates a three-dimensional model full laying path by generating a plurality of slice planes or surfaces after slicing the three-dimensional model, and then generating paths on the slice surfaces in sequence, it is only applicable to parametric three-dimensional models with simple geometric structures. In the face of complex non-parametric special-shaped surface three-dimensional models such as aero-engine fan blades, the slicing process is difficult to implement, so it is impossible to accurately generate a three-dimensional model full laying path. The present application generates a neutral surface based on the boundary surface information of the three-dimensional model, generates a fiber laying path on the neutral surface, and then offsets and filters the path by mirror image until the entire three-dimensional model is fully laid. Therefore, the present application does not need to slice the model, the path generation process is more optimized, and it is universal for complex non-parametric three-dimensional models. In addition, the strategy of generating a fiber laying path from the neutral surface to the two side boundary surfaces of the model proposed by the present application has the mirror image symmetry characteristic, which is completely consistent with the process characteristics of the mirror image fiber laying process from the neutral surface to the two side layers. The existing path generation method starts from the single side boundary surface of the model and generates in one direction, and the generated full laying path does not have the mirror image symmetry characteristic, which cannot meet the requirement of the mirror image fiber laying process that the fiber laying path needs to have the mirror image symmetry characteristic. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a flowchart of the present application;

[0018] Figure 2 It is a three-dimensional model of an aero-engine fan blade;

[0019] Figure 3 It is a fiber laying reference boundary surface diagram of a fan blade;

[0020] Figure 4 It is a diagram of two fiber laying reference boundary surfaces extracted in the form of triangular meshes;

[0021] Figure 5 a neutral surface graph generated based on two filament winding reference boundary surfaces;

[0022] Figure 6 a filament winding path graph generated on the neutral surface;

[0023] Figure 7 a schematic graph for a mirror image offset path;

[0024] Figure 8 a mirror image path graph generated when the offset distance is set to 5;

[0025] Figure 9 a mirror image path graph generated when the offset distance is set to 50;

[0026] Figure 10 a schematic graph for a path outside the filament winding reference boundary surface when the offset distance is 5;

[0027] Figure 11 a filtered mirror image filament winding path when the offset distance is 5;

[0028] Figure 12 a schematic graph for generating and filtering all mirror image paths of a blade model when the filament winding layer thickness is 0.5;

[0029] Figure 13 a comparison result of the applicability of generating different mirror image full-filling paths of three-dimensional models by a traditional method and the present application. DETAILED DESCRIPTION

[0030] The present embodiment is directed to a three-dimensional model path generation process for a moldless mirror image filament winding manufacturing process of a three-dimensional component represented by a fan blade of a carbon fiber composite material of Aero Engine, as shown in Figure 2 The whole process not only does not need to slice the three-dimensional model, solves the problem of difficult or inefficient slicing of complex three-dimensional models, but also generates a filament winding path that meets the mirror image symmetry requirement of the moldless mirror image filament winding process, as shown in Figure 1 specifically includes:

[0031] Step one, extracting a three-dimensional model filament winding reference boundary surface: for a three-dimensional model that needs to generate a path, a filament winding reference boundary surface is extracted, which is determined according to the filament winding requirement. For a fan blade model as shown in Figure 2 The filament winding surface is arranged along the thickness direction of the model, so the filament winding reference boundary surface is the outer surface on both sides of the model thickness, as shown in Figure 3

[0032] ​The extraction of the filament laying reference boundary surface in the embodiment is performed by calling the Spaceclaim 2019R1 software through the python code. The filament laying reference boundary surface can be directly separated from the three-dimensional model by calling the Spaceclaim 2019R1 software. As shown in Figure 4 , the two separated filament laying reference boundary surfaces maintain the spatial positional relationship on the three-dimensional model. Then, the two separated filament laying reference boundary surfaces are saved in the form of mesh surface for subsequent surface information extraction and calling. The two separated filament laying reference boundary surfaces can be saved in the form of stl, obj, ply, vtk and other types of triangular mesh surface format files.

[0033] Step two, generating a neutral surface in the three-dimensional model, specifically comprising:

[0034] 2.1 reading the triangular mesh element node coordinates, node numbers and triangular mesh element numbers of the filament laying reference boundary surface, based on the read reference surface node coordinates;

[0035] 2.2 using the Python library function KDTree to find the nearest point pair between the two surfaces, and calculating the midpoint, then defining the topology of the neutral surface based on the midpoint coordinate set using the same polygon structure as the reference surface, generating a mesh surface format neutral surface, as shown in Figure 5 ;

[0036] 2.3 calculating the normal vector of each triangular mesh element based on the surface mesh information for subsequent mirror path generation step calling.

[0037] Step three, as shown in Figure 6 , the neutral surface filament laying path is generated by using but not limited to the fixed angle method or the variable angle method.

[0038] The fixed angle method uses but is not limited to the technology recorded in Shirinzadeh B, Cassidy G, Oetomo D, et al. Trajectory generation for open-contoured structures in robotic fibre placement [J]. Robotics and Computer-Integrated Manufacturing, 2007, 23(4): 380-394.

[0039] The variable angle method adopts but is not limited to the technology recorded in Rousseau G, Wehbe R, Halbritter J, et al. Automated Fiber Placement Path Planning: A state-of-the-art review [J]. Computer-Aided Design and Applications, 2019, 16(2): 172-203.

[0040] Step four, generating mirror image offset path: based on the normal vector of each triangular mesh element on the neutral surface obtained in step two, offset the path points on the neutral surface obtained in step three along the normal direction of the triangular mesh element where the path point is located, and mirror image offset the path points to both sides of the neutral surface according to the mirror image offset distance, that is, offset the path points along the normal positive direction and the normal negative direction of the mesh element where the path point is located, respectively, to obtain the mirror image offset path, as shown in Figure 7 .

[0041] The mirror image offset distance D = d*i, wherein: d is the fiber laying layer thickness, and i is the mirror image offset cycle number; for example, when the mirror image offset path is generated for the first time, the offset distance is the fiber laying layer thickness, and when the mirror image offset path is generated for the second time, because there is one fiber laying layer on each side of the neutral surface, the offset distance is twice the fiber laying layer thickness, that is, d*2; that is, the mirror image offset distance is the product of the fiber laying layer thickness and the mirror image offset cycle number.

[0042] As shown in Figure 8 , the mirror image offset path generated when the mirror image offset distance is set to 5 is shown, in order to more conveniently display the mirror image offset path; as shown in Figure 9 , the mirror image path generated when the offset distance is set to 50 is shown, and it can be more obviously seen that the path is distributed on both sides of the neutral surface.

[0043] Step five, filtering the path located outside the three-dimensional model to ensure that the generated mirror image path is complete and accurate and covers the three-dimensional model, specifically: based on the mirror image offset path generated in step four, by checking the relative position of the mirror image path point and the three-dimensional model fiber laying reference boundary surface, only the path points located between the two reference surfaces are retained, the path points outside the two reference surfaces are removed, and the mirror image laying path is obtained.

[0044] As shown in Figure 10 , the mirror image path (the path visible on the right half) that needs to be filtered out when the given mirror image offset distance is 5 is shown, Figure 10The left half of the middle shows the complete mirror filaments path, and the right half shows the mirror path after introducing the filaments reference boundary surface. The visible path indicates that these paths are outside the filaments reference boundary surface, i.e. outside the three-dimensional model, so these visible paths will be filtered out, and only the paths inside the three-dimensional model will be retained.

[0045] As shown in Figure 11 , the filtered mirror filaments path, Figure 11 The left half shows the path outside the three-dimensional model before filtering, and the right half shows the path after filtering and removing the reference surface. The path on the right is the final mirror filaments path after filtering generated at a preset offset distance of Figure 11 5.

[0046] Step six, generate mirror paths that fill the three-dimensional model: according to the filaments angle requirements of the next mirror filaments layer, regenerate the neutral surface filaments path and set the mirror offset distance, repeat steps four and five until all the generated new mirror paths are outside the two filaments reference boundary surfaces of the three-dimensional model, i.e. stop the loop when the remaining path points after step five filtering are zero. At this time, all the generated mirror paths are the filaments paths that fill the entire three-dimensional model.

[0047] As shown in Figure 12 , the left half is a diagram of multiple mirror paths generated when the filaments layer thickness is 0.5 and the number of layers is 30. The left half of the diagram has blue paths outside one side of the filaments reference boundary surface and green paths outside the other side of the filaments reference boundary surface. These visible paths are outside the filaments reference boundary surface and do not belong to the three-dimensional model, i.e. they are not the required paths for the filaments process, so they need to be filtered out. The right half is a diagram after filtering these paths. The paths outside the two filaments reference boundary surfaces are all filtered out, i.e. only the paths inside the filaments reference boundary surface are retained. At this time, the paths are the full filaments paths of the three-dimensional model.

[0048] As shown in Figure 13 , for non-parametric non-uniform thickness three-dimensional models such as revolution bodies, aero-engine fan blades, Bezier surface bodies, and circular arc surface bodies, the applicability of the traditional path generation method and the present invention is compared. The traditional method of first slicing and then generating paths cannot generate mirror full filaments paths for the above-mentioned non-parametric models because it cannot mirror slice the three-dimensional model. The present invention does not need to slice the three-dimensional model and can directly optimize the generation of mirror full filaments paths for the three-dimensional model. The generated mirror full filaments paths are shown in Figure 13 .

[0049] The present application is aimed at the characteristics of mirror image filament laying process of two-sided simultaneous symmetrical filament laying, in order to solve the problem of full laying path optimization generation of three-dimensional model with non-parametric surface boundary, a path generation strategy is proposed, which firstly generates a neutral surface based on the model boundary surface information, then generates the filament laying path on the neutral surface, then offsets the neutral surface path to the two side boundary surfaces, and finally filters the offset mirror image path until the full laying path of the three-dimensional model is generated, the present application does not need to slice the model, the path generation process is more optimized, and it is universal for complex non-parametric three-dimensional models. In addition, the strategy of the present application for generating the filament laying path from the neutral surface to the two side filament laying reference boundary surfaces of the model has the characteristics of mirror image symmetry, which meets the process characteristic requirement of the mirror image filament laying process starting from the neutral surface to the two sides of the laying layer, while the existing path generation method starts from the single side boundary surface of the model to generate the path in one direction, and the generated full laying path does not have the characteristics of mirror image symmetry, which cannot meet the requirement of mirror image filament laying process that the filament laying path needs to have the characteristics of mirror image symmetry.

[0050] The above specific implementation can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present application, the protection scope of the present application is subject to the claims and is not limited by the above specific implementation, each implementation scheme within the scope is subject to the present application.

Claims

1. A method for generating a full-lay path for a three-dimensional model of patternless mirror-image wire laying, characterized in that: After determining the reference surface for 3D model placement based on model features and placement requirements and generating a neutral surface, the generated neutral surface placement path is used as the basis for cyclic mirror offset and filtering to generate a full placement path for the 3D model. The neutral plane is generated by determining the 3D model wire laying reference boundary surface based on the wire laying direction in the imported 3D model, converting the solid model of the wire laying reference boundary surface into a triangular mesh surface model, extracting the triangular mesh information of the wire laying reference boundary surface, and then generating a neutral plane equidistant from the two wire laying reference boundary surfaces based on the mesh node number, node coordinates, mesh unit number and mesh unit normal vector. Specifically, the neutral plane includes: Step 1: Extract the 3D model's reference boundary surface for placing wires: For the 3D model that requires path generation, extract the reference boundary surface for placing wires. The reference boundary surface is determined based on the placing requirements. For the fan blade model, the placing surface is arranged along the model's thickness direction, so the reference boundary surface is the outer surface on both sides of the model's thickness. Step 2: Generate the neutral surface of the 3D model, including: 2.1 Read the triangular mesh unit node coordinates, node number, and triangular mesh unit number of the fiber placement reference boundary surface based on the read reference surface node coordinates; 2.2 Use the Python library function KDTree to perform nearest neighbor search, find the closest point pair between the two surfaces, and calculate the midpoint. Then, based on the midpoint coordinate set, use the same polygon structure as the reference surface to define the topology of the neutral surface, and generate the neutral surface in mesh surface format; 2.3 Calculate the normal vector of each triangular mesh element based on the surface mesh information for subsequent mirror path generation steps; Step 3: Generate a neutral plane laying path using a fixed angle method or a variable angle method; Step 4: Generate a mirror offset path: Based on the normal vector of each triangular mesh unit on the neutral surface obtained in step 2, offset the path point on the neutral surface obtained in step 3 along the normal direction of the triangular mesh unit where the path point is located. Mirror the path point to both sides of the neutral surface according to the mirror offset distance, that is, offset the path point along the positive and negative normal directions of the mesh unit where it is located, respectively, to obtain a mirror offset path. Step 5: Filter the paths outside the 3D model to ensure that the generated mirror path completely and accurately lays the entire 3D model. Specifically, based on the mirror offset path generated in step 4, check the relative positions of the mirror path points and the reference boundary surfaces of the 3D model for laying. Only the path points between the two reference surfaces are retained, and the path points outside the two reference surfaces are removed to obtain the mirrored laying path. Step 6. Generate a mirror path that fills the entire 3D model: Based on the wire laying angle requirements for the next mirror layer, regenerate the neutral plane wire laying path and set the mirror offset distance. Repeat steps 4 and 5 until all the newly generated mirror paths are outside the two wire laying reference boundary surfaces of the 3D model. That is, the loop stops when the number of remaining path points in the new mirror path after filtering in step 5 is 0. At this point, all the generated filtered mirror paths are the wire laying paths that fill the entire 3D model. The mirror offset distance D=d*i, where d is the thickness of the fiber placement layer and i is the number of mirror offset cycles. For example, when a mirror offset path is generated for the first time, the offset distance is the thickness of the fiber placement layer. When a mirror offset path is generated for the second time, since there is a layer on each side of the neutral plane, the offset distance this time is twice the thickness of the fiber placement layer, i.e., d*2. That is, the mirror offset distance is the product of the fiber placement layer thickness and the number of mirror offset cycles.

2. The method for generating a full-lay path of a three-dimensional model of patternless mirror-image fiber placement according to claim 1 is characterized in that: The neutral plane laying path is generated based on the generated neutral plane triangular mesh unit information, and the neutral plane laying path is generated by the intersection method of the equidistant plane and the neutral plane. The equidistant plane is generated by giving the laying reference axis, laying angle and laying width, and the intersection points of the equidistant plane and each triangular mesh unit of the neutral plane are calculated. The intersection points are sorted and the path is smoothed to generate the path on the neutral plane.

3. The method for generating a full-lay path of a three-dimensional model of patternless mirror-image fiber placement according to claim 1 is characterized in that: The mirror offset is to perform mirror equidistant offset on the path point on the neutral plane along the normal positive direction and the normal negative direction of the triangular unit where the path point is located according to the preset layer thickness.

4. The method for generating a full-lay path of a three-dimensional model of patternless mirror-image fiber placement according to claim 1 is characterized in that: The filtering process determines the relative position between the generated mirrored wire placement path points and the wire placement reference plane, filters the generated mirrored wire placement path, removes the path points located outside the two wire placement reference boundary surfaces, and retains only the path points located on or within the two wire placement reference boundary surfaces.

5. The method for generating a full-lay path of a three-dimensional model of patternless mirror-image fiber placement according to claim 1 is characterized in that: The above-mentioned cycle is carried out, and the mirror offset distance is gradually increased according to the layer thickness. A new mirrored wire laying path is generated and then filtered until all path points on the newly generated mirrored path are located outside the two wire laying reference boundary surfaces. At this time, all the generated filtered mirrored wire laying paths can accurately lay out the three-dimensional model.

6. A system for generating a full-lay path of a three-dimensional mirror-shaped fiber placement model without a mold, which implements the method according to any one of claims 1 to 5, characterized in that: include: 3D model processing module, neutral surface generation module, neutral surface path generation module, mirror path generation and filtering module, 3D model full paving path generation module, wherein: the 3D model processing module imports and pre-processes the 3D model of the manufactured component; the neutral surface generation module determines the reference boundary surface of the laying wire based on the 3D model characteristics, and converts the surface solid model into a triangular mesh model, and extracts the triangular mesh information of the reference surface; based on the mesh information, a neutral surface equidistant from the two laying wire reference boundary surfaces is generated; the neutral surface path generation module generates the neutral surface laying wire path based on the generated neutral surface triangular mesh unit information, using the equidistant plane and neutral surface intersection method, generates the equidistant plane based on the control parameters and calculates the intersection point of the equidistant plane and each triangular mesh unit of the neutral surface, The intersection points are sorted and the paths are smoothed to generate the paths on the neutral surface; the mirror path generation and filtering module performs mirror equidistant offset on the path points on the neutral surface along the positive and negative normal directions of the triangular unit where the path points are located according to the preset layer thickness, and judges the relative position between the generated mirrored wire laying path points and the wire laying reference plane during the offset process, and filters the generated mirrored wire laying path to remove the path points outside the two wire laying reference boundary surfaces and only retain the path points inside the two wire laying reference boundary surfaces; the 3D model full laying path generation module gradually increases the offset distance according to the preset layer thickness, cyclically generates and filters the mirrored paths until all the generated mirrored paths are outside the 3D model, thereby generating the full laying path of the 3D model; The control parameters include: wire laying reference axis, wire laying angle, wire laying width, shortest wire laying path length, and minimum wire laying path curvature radius.

7. The system for generating a full-lay path for a three-dimensional model of patternless mirror-image fiber placement according to claim 6 is characterized in that: The preprocessing includes: importing, checking, repairing, translating, rotating, zooming in and out, switching views, color rendering, determining the wire laying reference boundary surface, extracting the triangular mesh information of the wire laying reference boundary surface, and storing the triangular mesh information of the wire laying reference boundary surface; The triangular mesh information includes: triangular mesh node number, node coordinates, mesh unit number, and mesh unit surface normal vector.

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