A method for generating trajectory of circular cutting machining based on surface area

Abstract

The present invention discloses a method for generating a surface region-based circular cutting machining trajectory, including using a mesh surface conformal mapping algorithm to map a three-dimensional surface to a plane parameter domain to obtain a flattened mesh region, calculating and saving the mapping deformation of each mesh face, clustering the mesh face; constructing a clustered boundary contour, and dividing the surface into a plurality of sub-surfaces according to the boundary contour; iterating the surface segmentation process so that the mapping deformation in each sub-surface tends to be consistent; obtaining a two-dimensional line spacing value of a point to be offset; generating a plane circular cutting trajectory on a plane mesh region of a sub-surface by offsetting according to the two-dimensional line spacing direction of the trajectory point and the adaptive two-dimensional line spacing value; inversely mapping the plane circular cutting trajectory back to a three-dimensional surface to obtain a three-dimensional circular cutting machining trajectory of the sub-surface; and further obtaining a three-dimensional circular cutting machining trajectory covering the original surface. The present invention has good spatial distribution uniformity.

Description

Technical Field

[0001] The invention relates to the field of mechanical processing, and in particular to a method for generating a curved surface area-divided circular cutting processing trajectory. Background Art

[0002] CNC machining is an important technical means to achieve high-quality and efficient machining of complex surfaces. In addition to high-performance CNC machine tools, machining tool paths are also a key factor affecting CNC machining efficiency and quality.

[0003] Generating tool paths on three-dimensional surfaces is exponentially more difficult than on planes or simple surfaces. It requires complex three-dimensional geometric calculations, and the algorithm has low stability. In addition, due to the complex shape and large curvature changes of three-dimensional surfaces, the distribution uniformity of complex surface machining trajectories is also difficult to control.

[0004] At present, the machining trajectory generation for complex surfaces is mostly based on sub-regions, because the sub-region trajectory generation method has more flexible applicability to complex surfaces than the overall planning method, and has significant advantages in reducing machining errors, improving machining efficiency, and improving feed motion stability. The tool path generation for mesh models based on mesh surface parameterization technology is also an emerging idea. The parametric mapping technology can reduce the dimension of complex three-dimensional geometric operations to the plane parameter domain, but there are also many problems in the actual application process. For example, the deformation of the parametric mapping will seriously affect the uniformity of the trajectory distribution. Summary of the invention

[0005] In order to solve the problem that the parametric mapping deformation affects the uniformity of trajectory distribution, the present invention provides a method for generating a surface area circular cutting processing trajectory. This method clusters and segments the surface using the mapping deformation as the grid feature, and improves the mapping deformation by iteratively trimming the surface multiple times. Then, according to the local geometric features of the sub-surface and the parametric mapping deformation, the mapping deformation compensation amount of the sub-surface and the line spacing value of the processing trajectory are adaptively adjusted. Finally, by improving the parametric quality of the surface and dynamically adjusting the trajectory parameters, the stability of the parametric mapping algorithm and the uniformity of the trajectory line spacing distribution are coordinated.

[0006] The present invention adopts the following technical solution:

[0007] A method for generating a surface region-by-region circular cutting machining trajectory based on conformal mapping deformation clustering includes the following specific steps:

[0008] (1) Extract the three-dimensional mesh surface information of the workpiece, map the three-dimensional mesh surface to the plane parameter domain through the mesh surface conformal mapping algorithm to obtain the flattened mesh area, and calculate and save the mapping deformation of each mesh face;

[0009] (2) clustering the plane meshes according to the mapping deformation of the mesh facets obtained in step (1);

[0010] (3) constructing a clustering boundary contour according to the grid clustering result generated in step (2), and dividing the surface into multiple sub-surfaces according to the boundary contour;

[0011] (4) for the multiple sub-surfaces obtained in step (3), recalculate their mapping deformation amounts, and continue to segment the sub-surfaces whose mapping deformation uniformity is lower than the uniformity threshold;

[0012] (5) Adaptively adjusting the two-dimensional line spacing value of the point to be offset on the circular cutting trajectory according to the mapped average tensile deformation of the sub-surface obtained in step (4) and the local geometric features of the surface corresponding to the point to be offset on the circular cutting trajectory, so that the line spacing of the circular cutting trajectory is evenly distributed on the three-dimensional surface;

[0013] (6) generating a plane circular cutting trajectory by offsetting the plane mesh area of ​​the sub-surface obtained in step (4) according to the adaptive two-dimensional line spacing value of the to-be-offset point calculated in step (5) to fill the entire plane mesh area;

[0014] (7) Inversely map the plane circular cutting trajectory generated in step (6) back to the three-dimensional surface to generate a three-dimensional circular cutting processing trajectory for each sub-surface.

[0015] (8) The sub-surface annular cutting processing trajectories generated in step (7) are sequentially connected together according to the adjacency relationship of each sub-surface, so as to generate a tool jumping trajectory connecting the annular cutting trajectories of different regions.

[0016] Furthermore, the mesh surface conformal mapping algorithm described in step (1) refers to a method for conformally mapping the mesh surface in three-dimensional space to a plane parameter domain, thereby establishing a one-to-one mapping relationship between the original three-dimensional surface mesh and the plane mesh in the parameter domain.

[0017] Furthermore, the mapping deformation amount in step (1) refers to the degree of deformation of the mesh face during the conformal mapping process of the mesh surface, and the deformation includes angle deformation, stretching deformation and area deformation.

[0018] Furthermore, the clustering described in step (2) refers to clustering and classification based on the relationship between the mapping deformation of the mesh face and the clustering initial value, wherein the clustering initial value is generally set to 0, and the mapping deformation greater than the clustering initial value is clustered into one category, and the mapping deformation less than or equal to the clustering initial value is clustered into one category.

[0019] Furthermore, the mapping deformation uniformity described in step (4) refers to the uniformity of the distribution of the mapping deformation amount within the mesh surface on the surface.

[0020] Furthermore, the uniformity threshold mentioned in step (4) refers to the boundary value determined according to the surface deformation and actual processing requirements for judging whether the surface mapping deformation is uniform or not, and the termination condition of the surface segmentation operation is that the surface mapping deformation uniformity is higher than the uniformity threshold.

[0021] Furthermore, the mapped average stretch deformation described in step (5) refers to the average level of the mapped stretch deformation in all directions within the mesh patch, and the mapped stretch deformation refers to the degree of length deformation generated by the mesh patch during the surface conformal mapping process, including stretch deformation and compression deformation, and the mapped stretch deformation is anisotropic on the mesh patch.

[0022] Furthermore, the mapped average tensile deformation in step (5) can be calculated as follows:

[0023]

[0024] Among them, σ ave is the average tensile deformation of the map, σ max is the maximum value of the anisotropic mapping tensile deformation, σ min The minimum value of the anisotropic mapping stretch deformation.

[0025] Furthermore, the two-dimensional line spacing value described in step (5) refers to the distance between corresponding trajectory points on two adjacent circular cutting tool tracks in the plane grid area, which is jointly determined by the residual height, tool geometry, local surface geometry information and grid conformal mapping stretching deformation; the two-dimensional line spacing value of each trajectory point on the regional circular cutting processing trajectory proposed in the present invention is variable, and the three-dimensional trajectory line spacing and material removal amount can be controlled by adjusting the two-dimensional line spacing value.

[0026] Furthermore, the two-dimensional line spacing value of the track point to be offset in the circular cutting track described in step (5) can be calculated by the following formula:

[0027]

[0028] Among them, l s is the two-dimensional line spacing value, h is the preset residual height value, r is the radius of the ball end cutter, ρ s is the normal curvature radius of the trajectory point to be offset in the three-dimensional line spacing direction. The positive sign is used when the trajectory point to be offset is located in a convex curvature, and the negative sign is used when the trajectory point to be offset is located in a concave curvature. ave _ max is the average tensile deformation σ of all meshes on the sub-surface aveAfter the iteration of the surface segmentation process in step (4), the distribution uniformity of the mapping deformation of the sub-surface is controlled within the uniformity threshold. Therefore, for the same sub-surface, the same mapping stretching deformation can be used to scale and compensate the trajectory parameters.

[0029] Furthermore, the step of generating the plane annular cutting trajectory in step (6) specifically includes:

[0030] (61) Select any closed loop curve on the plane grid area as the initial loop cutting trajectory;

[0031] (62) calculating the two-dimensional line spacing value of each discrete trajectory point on the circular cutting trajectory according to the local geometric information of the surface corresponding to the discrete trajectory point on the circular cutting trajectory, the preset residual height, the tool geometry and the grid conformal mapping deformation;

[0032] (63) According to the two-dimensional line spacing direction and the adaptive two-dimensional line spacing value of each discrete trajectory point, the corresponding trajectory point in the next loop is obtained by an offset method, and the trajectory points obtained by the offset are connected to obtain the trajectory of the next loop, wherein the two-dimensional line spacing direction is directly taken as a direction perpendicular to the two-dimensional feed direction;

[0033] (64) Repeat steps (62) and (63) to generate a circular cutting trajectory that can fill the entire plane grid area.

[0034] Furthermore, the specific steps of generating the tool jumping trajectory connecting the circular cutting trajectories of different regions in step (8) include:

[0035] (81) Traversing all sub-surfaces by depth-first traversal or breadth-first traversal based on the sub-surface adjacency matrix, and preserving the traversal order of the sub-surfaces;

[0036] (82) According to the sub-surface traversal order obtained in step (81), insert the jump tool trajectory between the two sub-surfaces in sequence.

[0037] Beneficial effects of the present invention:

[0038] This method uses the mapping deformation as the grid feature to cluster and segment the surface. Through the iterative clipping process, the parametric quality of the surface is effectively improved, and the parametric mapping deformation of the surface is significantly reduced. Then, according to the local geometric characteristics of the sub-surface and the parametric mapping deformation, the mapping deformation compensation amount of the sub-surface and the line spacing value of the circular cutting processing trajectory are adaptively adjusted, and the line spacing of the generated circular cutting trajectory can adapt to the geometric characteristics of the surface. By improving the parametric quality of the surface and dynamically adjusting the trajectory parameters, the stability of the parametric mapping algorithm and the uniformity of the trajectory line spacing distribution are coordinated, and the application value of the trajectory generation method based on mesh surface parameterization is improved, which has good spatial distribution uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a work flow chart of the present invention;

[0040] Figure 2 is a schematic diagram of a three-dimensional mesh surface model of the present invention;

[0041] Figure 3 is a schematic diagram of a flattened mesh area obtained by the mesh surface conformal mapping algorithm of the present invention;

[0042] Figure 4 It is a schematic diagram of simulation of mapping tensile deformation of the mesh surface of the present invention;

[0043] Figure 5 is a schematic diagram of the segmentation result of the mesh surface of the present invention;

[0044] Figure 6 It is a schematic diagram of calculating the two-dimensional line spacing value of the present invention;

[0045] Figure 7 Schematic diagram of the circular cutting trajectory generated on the plane mesh area of ​​the sub-surface S1 of the present invention

[0046] Figure 8 It is a schematic diagram of the annular cutting trajectory generated on the plane mesh area of ​​the sub-surface S2 of the present invention.

[0047] Fig. 9 It is a schematic diagram of the annular cutting trajectory generated on the plane mesh area of ​​the sub-surface S3 of the present invention.

[0048] Fig.10 It is a schematic diagram of the circular cutting trajectory generated on the three-dimensional mesh surface model of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0050] Example

[0051] like Figure 1 As shown, a method for generating a surface area circular cutting machining trajectory includes the following specific steps:

[0052] (1) Figure 2 The 3D mesh surface model of the workpiece shown is imported into the CAM software.

[0053] (2) The three-dimensional mesh surface is mapped to the plane parameter region through the mesh surface conformal mapping algorithm to obtain the flattened mesh region, such as Figure 3As shown, a one-to-one mapping relationship between the spatial grid and the plane grid is established. The grid surface conformal mapping algorithm includes, but is not limited to, the angle-preserving mapping method used in this example.

[0054] (3) Calculate and save the mapping deformation amount generated by each mesh patch during the parameterization process. The mapping deformation amount includes, but is not limited to, the mapping stretch deformation amount used in this example. The simulation diagram of the mapping stretch deformation amount L2 of the mesh patch is shown in FIG. Figure 4 shown.

[0055] (4) Clustering the plane meshes according to the mapping deformation of the mesh patch obtained in step (3), constructing the cluster boundary contour, dividing the surface into multiple sub-surfaces according to the boundary contour, and continuing to iteratively divide the sub-surfaces whose mapping deformation uniformity is lower than the uniformity threshold. Figure 5 It is a schematic diagram of the segmentation result of the mesh surface. Figure 5 Cluster boundary 1 and cluster boundary 2 shown by the thick lines in the middle divide sub-surface S1 and sub-surface S3, and sub-surface S2 and sub-surface S3 respectively. The uniformity of the mapping deformation within the three sub-surfaces S1, S2, and S3 is higher than the uniformity threshold, that is, the difference in the mapping deformation distribution of the grid is weaker.

[0056] (5) A closed-loop curve is randomly selected on the plane mesh area as an initial loop cutting trajectory. The initial loop cutting trajectory includes, but is not limited to, the surface contour curve used in this example.

[0057] (6) According to the local geometric information of the surface corresponding to the discrete trajectory points on the initial circular cutting trajectory selected in step (5), the preset residual height, the tool geometry and the grid conformal mapping deformation, the two-dimensional line spacing value of each discrete trajectory point on the circular cutting machining trajectory is calculated, so that the line spacing of the circular cutting trajectory is evenly distributed on the three-dimensional surface. The two-dimensional line spacing value can be calculated by the following formula:

[0058]

[0059] Among them, l s is the two-dimensional line spacing value, h is the preset residual height value, r is the radius of the ball end cutter, ρ s is the normal curvature radius of the trajectory point to be offset in the three-dimensional line spacing direction. The positive sign is used when the trajectory point to be offset is located in a convex curvature, and the negative sign is used when the trajectory point to be offset is located in a concave curvature. ave_max is the average tensile deformation σ of all meshes on the sub-surface ave The maximum value of Figure 6 It is a schematic diagram of two-dimensional line spacing value calculation.

[0060] (7) According to the two-dimensional line spacing direction and the adaptive two-dimensional line spacing value of each discrete trajectory point calculated in step (6), the corresponding trajectory point in the next loop is obtained by the offset method, and the trajectory points obtained by the offset are connected to obtain the trajectory of the next loop, wherein the two-dimensional line spacing direction is directly taken as the direction perpendicular to the two-dimensional feed direction.

[0061] (8) Repeat steps (6) and (7) to generate a plane circular cutting trajectory to fill the entire plane grid area. Figure 7 , Figure 8 and Fig. 9 Schematic diagrams of the circular cutting trajectories generated on the planar mesh areas of sub-surfaces S1, S2 and S3 respectively.

[0062] (9) Inversely map the plane circular cutting trajectory generated in step (8) back to the three-dimensional surface to generate a three-dimensional circular cutting processing trajectory for each sub-surface.

[0063] (10) Sort the sub-surface annular cutting processing trajectories generated in step (9) according to the adjacency relationship of each sub-surface, and insert the jump tool trajectory between two sub-surfaces in sequence to obtain the three-dimensional surface area annular cutting processing trajectory, such as Fig.10 As shown, the sorting method of the sub-surface circular cutting processing trajectory includes, but is not limited to, the depth-first traversal algorithm used in this example.

[0064] The present invention clusters and segments the surface with the goal of uniform distribution of conformal mapping deformation, and then adaptively adjusts the two-dimensional row spacing value of the point to be offset on the annular cutting trajectory according to the local geometric features of the segmented surface and the conformal mapping stretching deformation. The row spacing of the generated regional annular cutting trajectory is adaptive to the local geometric shape of the surface, thereby having better spatial distribution uniformity.

[0065] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for generating a surface area circular cutting machining trajectory, characterized in that: include: Input the 3D mesh surface information of the workpiece, map the 3D mesh surface information to the plane parameter domain through the mesh surface conformal mapping algorithm, obtain the flattened mesh area, calculate and save the mapping deformation of each mesh face; According to the mapping deformation of each mesh patch, the plane mesh is clustered, the cluster boundary contour is further constructed, and the surface is divided into multiple sub-surfaces according to the boundary contour; For multiple sub-surfaces, the corresponding mapping deformation amounts are recalculated, and the sub-surfaces whose mapping deformation uniformity is lower than the uniformity threshold are iterated until the mapping deformation uniformity of all sub-surfaces is higher than the uniformity threshold; According to the average tensile deformation of each sub-surface and the local geometric features of the surface corresponding to the point to be offset on the annular cutting trajectory, the two-dimensional line spacing value of the point to be offset is obtained; According to the two-dimensional line spacing value of the point to be offset, a plane circular cutting trajectory is generated on the plane mesh area of ​​the sub-surface by offsetting to fill the entire plane mesh area; Inversely map the generated plane circular cutting trajectory back to the three-dimensional surface to generate the three-dimensional circular cutting processing trajectory of each sub-surface; Connect the three-dimensional circular cutting machining tracks generated in the previous step in sequence according to the adjacency relationship of each sub-surface to generate circular cutting machining tracks connecting different regions; The generated plane annular cutting trajectory is specifically: Select any closed loop curve on the plane grid area as the initial loop cutting trajectory; Calculate the two-dimensional line spacing value of each discrete track point on the circular cutting trajectory according to the local geometric information of the surface corresponding to the discrete track point on the circular cutting trajectory, the preset residual height, the tool geometry and the grid conformal mapping deformation; According to the two-dimensional spacing direction and the adaptive two-dimensional spacing value of each discrete trajectory point, the corresponding trajectory point in the next loop is obtained by the offset method, and the trajectory points obtained by the offset are connected to obtain the trajectory of the next loop, wherein the two-dimensional spacing direction is directly taken as the direction perpendicular to the two-dimensional feeding direction; Generate a circular cutting trajectory that can fill the entire planar mesh area; The generating of the circular cutting processing trajectory connecting different regions specifically includes: Traverse all sub-surfaces by depth-first traversal or breadth-first traversal based on the sub-surface adjacency matrix, and save the traversal order of the sub-surfaces; According to the sub-surface traversal order obtained in the previous step, insert the jump tool trajectory between the two sub-surfaces in turn.

2. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The mesh surface conformal mapping algorithm specifically adopts an angle-preserving mapping method.

3. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The mapping deformation uniformity refers to the uniformity of the distribution of the mapping deformation amount within the mesh surface on the surface.

4. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The mapped average stretch deformation refers to the average level of the mapped stretch deformation in each direction within the mesh patch. The mapped stretch deformation refers to the degree of length deformation generated by the mesh patch during the surface conformal mapping process. The length deformation includes stretch deformation and compression deformation. The mapped stretch deformation is anisotropic on the mesh patch.

5. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The two-dimensional line spacing value of the point to be offset is specifically obtained by the following formula: Among them, l s is the two-dimensional line spacing value, h is the preset residual height value, r is the radius of the ball end cutter, ρ s is the normal curvature radius of the trajectory point to be offset in the three-dimensional line spacing direction. The positive sign is used when the trajectory point to be offset is located in a convex curvature, and the negative sign is used when the trajectory point to be offset is located in a concave curvature. ave_max is the average tensile deformation σ of all meshes on the sub-surface ave The maximum value of .

6. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The clustering refers to clustering and classification based on the size relationship between the mapping deformation of the mesh surface and the clustering initial value, wherein the clustering initial value is set to 0, and the mapping deformation greater than the clustering initial value is clustered into one category, and the mapping deformation less than or equal to the clustering initial value is clustered into one category.

7. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 6, characterized in that: For the same plane, the same mapping stretching deformation is used to scale and compensate the estimated parameters.

8. The method for generating a curved surface region-by-region circular cutting machining trajectory according to claim 1, characterized in that: The two-dimensional line spacing value of each track point on the regional circular cutting processing track is variable, and the three-dimensional track spacing and material removal amount can be controlled by adjusting the two-dimensional line spacing value.

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