Three-dimensional curved surface pattern layering processing method based on parameterized segmentation

Abstract

The invention discloses a three-dimensional curved surface pattern layering processing method based on parameterized segmentation, and aims to solve the problem of high-precision pattern processing on the surface of a curved surface by using a laser scanning galvanometer. The method comprises the following steps: firstly, importing a three-dimensional model, and carrying out parameterization processing to obtain a two-dimensional parameter domain; positioning a to-be-processed plane pattern in the two-dimensional parameter domain to form a complete two-dimensional geometric grid covering a pattern area, generating a three-dimensional pattern grid attached to a curved surface, and calculating a center normal vector of the three-dimensional pattern grid; then, generating an equidistant plane group on the surface of the curved surface, and calculating an intersection line of the plane and the three-dimensional pattern grid as a laser scanning track; and the five-axis linkage platform-galvanometer system is started for machining. Through the parameterization domain, distortion of curved surface pattern machining is effectively solved, machining uniformity is improved, and the method is particularly suitable for laser machining of large-scale or high-complexity curved surface patterns.

Description

Technical Field

[0001] This invention relates to the field of laser surface processing, and more specifically to a method for layered processing of three-dimensional surface patterns based on parametric segmentation. Background Technology

[0002] A laser galvanometer machining system mainly consists of a laser, a galvanometer scanning system, and a control system. The laser generates laser light, the control system processes the pattern and its filling shape, and sends control commands to the galvanometers, causing the two galvanometers to swing at specific angles, thereby changing the reflection direction of the laser beam and enabling the laser beam to scan rapidly within the processing plane to achieve workpiece processing.

[0003] However, traditional laser scanning galvanometers have limitations when machining curved surfaces. Currently, there are several effective methods for using galvanometers for curved surface machining: 1) Employing a three-dimensional galvanometer with added Z-axis control functionality, allowing adjustment of the laser beam focus based on changes in surface height; 2) Combining robotics technology, utilizing the high flexibility and multi-degree-of-freedom motion of robots to adjust the spatial position and orientation of the galvanometer, ensuring the laser incident angle and focal offset distance; 3) Incorporating multi-axis linkage technology, adding rotary or linear axes to the original X and Y axes of the galvanometer to construct a multi-axis linkage system, such as a five-axis linkage system where each axis moves collaboratively to dynamically adjust the workpiece or laser processing head orientation.

[0004] Among these methods, the galvanometer system combined with a five-axis system typically offers high motion accuracy while allowing for flexible adjustment of spatial attitude. However, current mainstream surface machining methods mainly involve dividing the surface to be machined into numerous smaller surfaces and treating these smaller surfaces as approximations of planes for machining. This method inevitably generates a large number of splicing areas and has low machining efficiency. At the splicing points, uneven machining results are difficult to avoid, severely affecting the overall quality of the machined surface and making it unsuitable for machining large, continuous curved surfaces.

[0005] To address the shortcomings of existing technologies, this invention provides a surface machining method based on a five-axis linkage platform and a laser scanning galvanometer. This method parameterizes the surface region to be machined, constructs a two-dimensional spatial triangular patch representation of the pattern, and obtains the surface pattern through inverse mapping, then performs layer-by-layer machining on it. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for layered processing of three-dimensional curved surface patterns based on parametric segmentation. This method parameterizes the surface to be processed onto a two-dimensional plane, performs pattern positioning and boundary reconstruction within the two-dimensional domain, generates an attached three-dimensional pattern mesh, and calculates the galvanometer scanning trajectory layer by layer.

[0007] A method for layered processing of three-dimensional curved surface patterns based on parametric segmentation, characterized by the following steps:

[0008] 1. A method for layered processing of three-dimensional curved surface patterns based on parametric segmentation, characterized by comprising the following steps:

[0009] (1) Import a three-dimensional model, parameterize the target processing area of ​​the three-dimensional model, generate its mapping relationship to the two-dimensional parameter domain, and obtain a two-dimensional plane mapping map.

[0010] (2) Two-dimensional pattern processing and boundary reconstruction:

[0011] (2.1) In the two-dimensional parameter domain, move, scale, or rotate the planar pattern to be processed to the specified area;

[0012] (2.2) Based on the boundary contour of the planar pattern, the triangular facets in the mapping map are classified and identified as internal triangular facets and edge triangular facets. The intersection of the edge triangular facets and the pattern contour is calculated. After the outer part of the pattern is cut off, the boundary polygon is reconstructed using constrained Delaunay triangulation (CDT).

[0013] (2.3) Triangulate the boundary polygons generated after cutting, merge the newly generated boundary triangular facets with the original internal triangular facets to form a two-dimensional geometric model covering the pattern area represented by a complete triangular mesh;

[0014] (3) The pattern triangular facets are back-mapped to three-dimensional space to obtain a three-dimensional pattern triangular mesh attached to the three-dimensional surface. The normal vectors of all triangular facets in the pattern area are calculated by weighted average method and normalized to serve as the normal vector of the pattern center.

[0015] (4) Rotate the three-dimensional pattern so that the normal vector is vertically upward. Find the highest vertex (maximum Z value) and lowest vertex (minimum Z value) along the vertical direction (Z axis) and record the corresponding points of these extreme points in the original three-dimensional model space and / or two-dimensional parameter domain.

[0016] (5) In the two-dimensional parameter domain, generate a set of equidistant points between the highest and lowest points with a specified step size;

[0017] (6) At the height of each point, calculate the intersection of the horizontal plane and the three-dimensional pattern as the laser scanning path;

[0018] (7) Start processing and wait for processing to complete.

[0019] Furthermore, in step (1):

[0020] If the target processing area is a closed surface or a part thereof, it needs to be preprocessed and segmented before parameterization in order to perform parameterization;

[0021] The surface to be processed satisfies the G1 curvature continuity condition;

[0022] The parameterization methods include, but are not limited to, ARAP parameterization, conformal mapping, and isometric mapping.

[0023] The three-dimensional model is stored in a triangular patch format, including but not limited to STL and OBJ formats.

[0024] Furthermore, in step (2), for large-scale curved surface patterns, the pattern can be divided into multiple sub-patterns, and processing operations can be performed on each pattern in turn.

[0025] Furthermore, in step (6), the calculated curve segments are sorted, connected, and curve interpolation is performed as needed to form the final laser scanning path of the planar layer.

[0026] Furthermore, in step (7):

[0027] The relative positions of the linkage platform coordinate system, workpiece coordinate system, and galvanometer coordinate system need to be determined, and coordinate transformation needs to be performed.

[0028] A five-axis machining platform is used, which is a rotary table type, a tilting head type, or a hybrid structure, and its rotary axis configuration includes at least one of the following combinations:

[0029] The C-axis about the Z-axis and the A-axis about the X-axis;

[0030] The C-axis around the Z-axis and the B-axis around the Y-axis;

[0031] The A-axis around the X-axis and the B-axis around the Y-axis;

[0032] The galvanometer system is configured as a two-dimensional scanning module or a three-dimensional galvanometer module integrating planar scanning components.

[0033] Furthermore, it also includes at least one of the following optical path configuration options:

[0034] Option 1: Flexible optical fiber transmission path, using single / multimode optical fiber with a core of 50–600μm, and a transmission wavelength range of 300–2100nm;

[0035] Option 2: Free space optical path, transmission wavelength range 200–2000nm.

[0036] Furthermore, the laser used is selected from at least one of the following types: fiber laser, semiconductor laser, solid-state laser, and CO2 laser.

[0037] Furthermore, the average output power of the laser ranges from 10W to 6000W.

[0038] Furthermore, the laser operates in either continuous mode or pulsed mode.

[0039] This invention discloses a method for layered processing of three-dimensional curved surface patterns based on parametric segmentation. This method parameterizes the surface to be processed onto a two-dimensional plane, performs pattern positioning and boundary reconstruction within the two-dimensional domain, generates an attached three-dimensional pattern mesh, calculates the scanning trajectory of a galvanometer layer by layer, and processes the three-dimensional curved surface pattern using a five-axis linkage platform in conjunction with a laser galvanometer. This invention has the following advantages:

[0040] 1. By adopting parameterization, pattern distortion (such as stretching, compression, and jagged edges) of traditional projection or mapping methods is effectively eliminated, ensuring high fidelity and contour boundary accuracy from the design pattern to the three-dimensional surface geometry mapping, which is especially suitable for application scenarios with high requirements for pattern details.

[0041] 2. The galvanometer system performs laser beam scanning motion within the layered cutting plane, making full use of the high-speed and flexible motion characteristics of the galvanometer to adjust the workpiece posture and working distance in five axes, thereby achieving curved surface machining without focal changes.

[0042] 3. For large-scale curved surfaces / patterns that exceed the effective field of view or incident angle limit of a single galvanometer, this method supports block segmentation of the pattern region. By independently parameterizing, reconstructing boundaries, planning layered paths, and processing partitions for each segmented sub-region, the incident angle of the laser beam can be controlled within the allowable range. Attached Figure Description

[0043] The present invention will now be described in detail with reference to the accompanying drawings. Wherein:

[0044] Figure 1 : This is a flowchart of the present invention.

[0045] Figure 2 : Schematic diagram of hemispherical plane segmentation, wherein the distances between the plane segmentation contours on the sphere are equal (circular arcs AB and BC have equal lengths). Detailed Implementation

[0046] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0047] The equipment of this invention is an existing laser processing equipment, mainly composed of a laser, a two-dimensional scanning galvanometer, and an XYZAC five-axis linkage platform.

[0048] Invention Example 1 (Fine Engraving on Curved Surfaces of Precious Metal Jewelry)

[0049] 1) Import the 3D model of an 18K gold ring (STL format). The main body of the ring is a closed topological toroidal surface. Cut and segment along the central symmetry plane of the ring to obtain two semi-cylindrical open surfaces. Use conformal mapping to parameterize one of the areas to be engraved into a 2D rectangular domain.

[0050] 2)(2.1) Translate and scale the rose plane vector pattern to the specified position on the ring surface within the two-dimensional parameter domain.

[0051] (2.2) Identify the intersection of the rose flower boundary and the grid: the inner leaf vein facet is marked as the inner triangular facet; the facet where the edge petal outline intersects with the grid boundary is marked as the edge triangular facet, and the latter is cut off to remove the excess part.

[0052] (2.3) Constrain the boundaries of the petal polygons generated after cutting by Delaunay triangulation, merge the new triangular facets with the original internal facets to form a complete two-dimensional triangular mesh of the rose.

[0053] 3) Using conformal inverse mapping, the vertices of the 2D mesh are inversely mapped to the ring surface to generate a 3D rose relief mesh. The area-weighted average normal vector of the mesh is calculated as the pattern center normal vector (pointing outward from the ring).

[0054] 4) Construct a rotation transformation matrix so that the normal vector is parallel to the Z-axis of the linkage platform (vertically upward). In the rotated 3D pattern, the stamen vertex is the highest point (Z_max = 12.5mm), and the bottom of the petals is the lowest point (Z_min = 11.8mm).

[0055] 5) Within the two-dimensional parameter domain, between the highest and lowest points, generate an equidistant point group with a step size δd = 0.02 mm, and map it to obtain the three-dimensional equidistant point group and its corresponding horizontal plane.

[0056] 6) Calculate the intersection line between each plane and the three-dimensional pattern mesh to generate the galvanometer scanning trajectory.

[0057] 7) Coordinate system association: The workpiece is clamped on the turntable (C-axis), the origin of the galvanometer coordinate system is aligned with the center of the turntable, and the A-axis (around the X-axis) is used to adjust the incident angle.

[0058] 8) Turn on the 20W fiber laser (λ=1064nm) and set the scanning speed to 2m / s. Rotate the ring along the C-axis to make the normal of the current processing area parallel to the Y-axis. Adjust the A-axis accordingly to make the laser perpendicular to the incident direction. The galvanometer executes the XY scanning path for this layer, and processes layer by layer with decreasing Z-axis speed.

[0059] Embodiment 2 of the Invention (QR code marking on the surface of turbine blades)

[0060] 1) Import the nickel-based alloy turbine blade model (OBJ format) and perform ARAP parameterization on the blade pressure surface to generate a low-twist two-dimensional mapping (non-closed surface, no segmentation required).

[0061] 2) Because the size of the QR code exceeds the field of view of the galvanometer, the pattern is divided into 4 sub-matrix blocks.

[0062] 3) For QR code block one, locate the local pattern of the QR code in the two-dimensional domain, identify and cut the edge triangular facets, triangularly divide the boundary, and merge them to obtain a two-dimensional grid.

[0063] 4) Obtain the 3D QR code mesh through inverse mapping, calculate the centroid normal vector of each vertex, and then rotate it to the vertical direction. Record the independent highest and lowest points of each sub-block.

[0064] 5) Set the step size δd = 0.05 mm, generate an equidistant point group between the highest and lowest points in the two-dimensional parameter plane, and map it to obtain a three-dimensional equidistant point group.

[0065] 6) For each 3D equidistant point, calculate the intersection line between the horizontal plane and the 3D QR code grid. After the intersection line of each layer is optimized by nearest neighbor connection, a laser path is generated to ensure continuous scanning without jumps.

[0066] 7) Use a dual-head five-axis linkage platform (A-axis around X, B-axis around Y), with the galvanometer being a three-dimensional module integrating Z-axis dynamic focusing. Fix the blade to the worktable and adjust it via the AB axes to make the pattern normal vector parallel to the Z-axis. The three-dimensional galvanometer performs XY scanning and dynamic focusing (maintaining a spot diameter of 50μm). After completing the sub-block, translate the blade and process the remaining three blocks according to the segmentation scheme.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for layered processing of three-dimensional curved surface patterns based on parametric segmentation, characterized in that, Includes the following steps: (1) Import a three-dimensional model, parameterize the target processing area of ​​the three-dimensional model, generate its mapping relationship to the two-dimensional parameter domain, and obtain a two-dimensional plane mapping map. (2) Two-dimensional pattern processing and boundary reconstruction: (2.1) In the two-dimensional parameter domain, move, scale, or rotate the planar pattern to be processed to the specified area; (2.2) Based on the boundary contour of the planar pattern, the triangular facets in the mapping map are classified and identified as internal triangular facets and edge triangular facets. The intersection of the edge triangular facets and the pattern contour is calculated. After the outer part of the pattern is cut off, the boundary polygon is reconstructed using constrained Delaunay triangulation (CDT). (2.3) Triangulate the boundary polygons generated after cutting, merge the newly generated boundary triangular facets with the original internal triangular facets to form a two-dimensional geometric model covering the pattern area represented by a complete triangular mesh; (3) The pattern triangular facets are back-mapped to three-dimensional space to obtain a three-dimensional pattern triangular mesh attached to the three-dimensional surface. The normal vectors of all triangular facets in the pattern area are calculated by weighted average method and normalized to serve as the normal vector of the pattern center. (4) Rotate the three-dimensional pattern so that the normal vector is vertically upward. Find the highest vertex (maximum Z value) and lowest vertex (minimum Z value) along the vertical direction (Z axis) and record the corresponding points of these extreme points in the original three-dimensional model space and / or two-dimensional parameter domain. (5) In the two-dimensional parameter domain, generate a set of equidistant points between the highest and lowest points with a specified step size; (6) At the height of each point, calculate the intersection of the horizontal plane and the three-dimensional pattern as the laser scanning path; (7) Start processing and wait for processing to complete.

2. The laser curved surface processing method according to claim 1, characterized in that, In step (1): If the target processing area is a closed surface or a part thereof, it needs to be preprocessed and segmented before parameterization in order to perform parameterization; The surface to be processed satisfies G 1 Curvature continuity condition; The parameterization methods include, but are not limited to, ARAP parameterization, conformal mapping, and isometric mapping. The three-dimensional model is stored in a triangular patch format, including but not limited to STL and OBJ formats.

3. The laser curved surface processing method according to claim 1, characterized in that, In step (2): For large-scale curved surface patterns, the pattern can be divided into multiple sub-patterns, and processing operations can be performed on each pattern in sequence.

4. The laser curved surface processing method according to claim 1, characterized in that, In step (6): The calculated curve segments are sorted, connected, and curve interpolation is performed as needed to form the final laser scanning path for the planar layer.

5. The laser curved surface processing method according to claim 1, characterized in that, In step (7): The relative positions of the linkage platform coordinate system, workpiece coordinate system, and galvanometer coordinate system need to be determined, and coordinate transformation needs to be performed. A five-axis machining platform is adopted, wherein the platform is a rotary table type, a tilting head type or a hybrid structure, and its rotation axis configuration includes at least one combination of the following: a C-axis around the Z-axis and an A-axis around the X-axis; The C-axis around the Z-axis and the B-axis around the Y-axis; The A-axis around the X-axis and the B-axis around the Y-axis; The galvanometer system is configured as a two-dimensional scanning module or a three-dimensional galvanometer module integrating planar scanning components.

6. The laser curved surface processing method according to claims 1 to 5, characterized in that, It also includes at least one of the following optical path configuration options: Option 1: Flexible fiber optic transmission path, using single / multimode fiber with a core of 50–600μm, and a transmission wavelength range of 300–2100nm; Option 2: Free space optical path, transmission wavelength range 200–2000nm.

7. The laser surface processing method according to any one of claims 1 to 6, characterized in that, The laser is selected from at least one of the following types: fiber laser, semiconductor laser, solid-state laser, and CO2 laser.

8. The laser curved surface processing method according to claim 7, characterized in that, The laser has an average output power range of 10W to 6000W. The laser curved surface processing method according to claim 7 is characterized in that, The laser operates in either continuous mode or pulsed mode.

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