Blank shape matching method for automobile mold NC machining

Abstract

The present invention relates to the field of blank data processing for CNC machining of automotive molds, and specifically to a blank shape matching method for CNC machining of automotive molds, which greatly improves the accuracy of blank data matching while reducing the benchmark error of CNC machining. The scheme includes: obtaining point cloud data of the structure and surface of the blank, obtaining the minimum outer envelope unit of the point cloud data, equally dividing and cutting the minimum outer envelope unit, deleting noise point cloud data, calculating the mean and standard deviation of the distance from the point cloud to the center point within the polyhedron unit, judging and processing the point cloud data based on the mean and standard deviation, combining STL data with the design model for comparison and processing, optimizing and improving the machining program, and importing it into the CNC machine tool program processing. After configuring the machine tool and tool according to the program, simulation inspection and simulation are performed. The present invention is suitable for blank data matching in CNC machining of automotive molds.

Description

Technical Field

[0001] The present invention relates to the field of blank data processing for numerically controlled machining of automobile molds, and in particular to a blank shape matching method for numerically controlled machining of automobile molds. Background Art

[0002] After the automobile mold design is completed, major large components such as the upper mold base, lower mold base, and presser need to be cast. The casting quality of the casting has an important impact on the CNC machining efficiency and accuracy of the mold. The current traditional method is to scan the casting through 3D laser scanning technology, and then compare it with the actual design data. After processing, the optimized machining blank data is formed. Therefore, ensuring that the blank's data scanning and processing accuracy matches the design data becomes critical for mold processing. Currently, the common practice is to use the laser scanning equipment's built-in software for scanning and processing. Automotive molds are custom-made, requiring complex curved surfaces, including the guide plate mounting surface, deadbolts, balance blocks, cam drive seats, and forming insert mounting surfaces. This is due to deviations from the design data during the blank casting process. Furthermore, factors such as the roughness and reflectivity of various blank components and the equipment's parameter settings can cause deviations in the scanned data during the 3D scanning process. If the scanned casting allowance exceeds the design allowance, machining risks such as excessive backcutting and even tool collisions are likely to occur. However, if the casting allowance is too small, overcutting defects can easily occur. Currently, the typical approach relies on the equipment's own software to perform optimal fitting and matching based on the scanned blank data and theoretical design data. Technicians then specify the reference values ​​for machining during programming, and operators infer the reference values ​​based on the process instructions. This results in low blank data fitting and matching accuracy and large reference errors during CNC machining. Summary of the Invention

[0003] The purpose of the present invention is to provide a blank shape matching method for automobile mold NC machining, which greatly improves the accuracy of blank data matching and reduces the reference error of NC machining.

[0004] The present invention adopts the following technical solutions to achieve the above-mentioned purpose, and the method for matching the blank shape in CNC machining of automobile molds comprises:

[0005] Step 1: Process the blank into a three-dimensional plane reference W, and perform a three-dimensional scan on the blank with W as the reference to obtain point cloud data of the blank's structure and surface;

[0006] Step 2: Mesh the point cloud data of the part to be processed and use the envelope command of the software to obtain the minimum outer envelope unit of the point cloud data;

[0007] Step 3, equally dividing the minimum outer envelope unit, specifically comprising: equally dividing the envelope into regular polyhedral units;

[0008] Step 4: Delete the noise point cloud data, specifically including: calculating the ratio of two adjacent polyhedral unit point clouds, the numbers of adjacent polyhedral unit point clouds are n1 and n2 respectively, if Then delete the n point cloud data in the previous unit body, λ is a positive number less than 1, and n, n1, and n2 are all integers greater than 0;

[0009] Step 5: Calculate the mean and standard deviation of the distance from the point cloud to the center point in the polyhedron unit. Specifically, if the center point coordinates of the polyhedron unit are (x0, y0, z0), the number of point clouds in a single unit is n, and the distance from the point cloud to the center point is

[0010] The mean of the distance The standard deviation of this distance

[0011] Step 6: Determination and processing of point cloud data, specifically including: Determine whether the point cloud data meets the blank processing accuracy, k is the mold blank processing accuracy coefficient; if the calculated distance d from the point cloud to the center point within the volume unit does not meet the range, the point cloud data is deleted and marked in the digital model structure, and finally an STL data file is generated;

[0012] Step 7: Compare and process the STL data with the design model, optimize and improve the machining program, and import it into the CNC machine tool program processing. After configuring the machine tool and tool according to the program, perform simulation inspection and simulation.

[0013] Furthermore, the regular polyhedral unit is a regular tetrahedral unit or a regular hexahedral unit.

[0014] The point cloud data of the surface structure of the male and female dies adopts tetrahedron elements, while the guide plate mounting surface, squat block, balance block, wedge drive seat, forming insert mounting surface and safety side pin processing surface structure adopt hexahedron elements.

[0015] Furthermore, the side length of the regular tetrahedral unit or regular hexahedral unit is l, n is the average number of points in a single polyhedral unit; ρ is the average density of the point cloud within the minimum outer envelope, ρ = N / (x max -x min )(y max -y min )(z max -z min ), N is the total number of point cloud data of the machining installation surface.

[0016] The present invention firstly processes a three-dimensional plane reference W on a CNC machine tool, and uses laser scanning software to scan the automobile mold casting with W as the scanning reference. The curved surface and plane processing areas are divided into tetrahedron and hexahedron units respectively, and the minimum outer envelope unit is cut into equal parts. Then, the distance from the center of the unit to the point cloud data is calculated, and the mean value d and standard deviation m of the distance are obtained. Determine whether the point cloud data meets the blank processing accuracy, mark and delete the non-compliant point cloud data, output the processed mesh file, compare and process the output STL data with the design model, optimize and improve the processing program, and import it into the CNC machine tool program processing. After configuring the machine tool and tool according to the program, perform simulation inspection and simulation, effectively ensuring the accuracy of the blank data matching the design data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a method for matching blank data provided by an embodiment of the present invention;

[0018] Figure 2 Schematic diagram of the distance from a point cloud to a center point within a tetrahedron or dihedron unit provided by an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of initial data after three-dimensional scanning of an automobile mold base provided by an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the blank processing data after matching the automobile mold base provided by an embodiment of the present invention.

[0021] In the accompanying drawings, 101 is a side reference. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] The present invention provides a method for matching the blank shape of automobile molds through numerical control machining, such as Figure 1 Shown, including:

[0024] Step 1: Process the blank into a three-dimensional plane reference W, and perform a three-dimensional scan on the blank with W as the reference to obtain point cloud data of the blank's structure and surface;

[0025] In one embodiment of the present invention, the initial data after the three-dimensional scanning of the automobile mold base is as follows: Figure 3 shown.

[0026] Step 2: Mesh the point cloud data of the part to be processed and use the envelope command of the software to obtain the minimum outer envelope unit of the point cloud data;

[0027] In one embodiment of the present invention, the regular polyhedral unit is a regular tetrahedral unit or a regular hexahedral unit.

[0028] The point cloud data of the surface structure of the male and female dies adopts tetrahedron elements, while the guide plate mounting surface, squat block, balance block, wedge drive seat, forming insert mounting surface and safety side pin processing surface structure adopt hexahedron elements.

[0029] Step 3, equally dividing the minimum outer envelope unit, specifically comprising: equally dividing the envelope into regular polyhedral units;

[0030] In one embodiment of the present invention, the side length of the regular tetrahedral unit or the regular hexahedral unit is l, n is the average number of points in a single polyhedral unit; ρ is the average density of the point cloud within the minimum outer envelope, ρ = N / (x max -x min )(y max -y min )(z max -z min ), N is the total number of point cloud data of the machining installation surface.

[0031] Step 4: Delete the noise point cloud data. Since there are gates, risers and some casting defects in the guide plate mounting surface, squat block, balance block, wedge drive seat, forming insert mounting surface, safety side pin and other parts during the casting process, in order to delete these features, the point cloud data deletion method specifically includes: calculating the ratio of two adjacent polyhedron unit point clouds, the number of adjacent polyhedron unit point clouds are n1 and n2 respectively, if Then delete the n point cloud data in the previous unit body, λ is a positive number less than 1, which can be an empirical value obtained based on the summary of previous scanning processes;

[0032] Step 5: Calculate the mean and standard deviation of the distance from the point cloud to the center point in the polyhedron unit. Specifically, if the center point coordinates of the polyhedron unit are (x0, y0, z0), the number of point clouds in a single unit is n, and the distance from the point cloud to the center point is as follows: Figure 2 As shown,

[0033] The mean of the distance The standard deviation of this distance

[0034] Step 6: Determination and processing of point cloud data. The distance d from the point cloud to the center point obeys the statistical normal distribution. Therefore, the determination method specifically includes: Determine whether the point cloud data meets the blank processing accuracy. k is the mold blank processing accuracy coefficient. For the convex and concave model surfaces, reference surfaces, and mating installation surfaces of automobile exterior panels, the K value is 1≤k≤1.5. For other non-important processing surfaces, the K value is 1.5<k≤2.

[0035] If the calculated distance d from the point cloud to the center point in the volume unit does not meet the range, the point cloud data is deleted and marked in the digital model structure, and finally an STL data file is generated, such as Figure 4 The figure shows the schematic diagram of the blank processing data after matching the automobile mold base.

[0036] Step 7: Compare and process the STL data with the design model, optimize and improve the machining program, and import it into the CNC machine tool program processing. After configuring the machine tool and tool according to the program, perform simulation inspection and simulation to effectively ensure the accuracy of the matching between the blank data and the design data.

[0037] In summary, the present invention greatly improves the accuracy of blank data matching, can control the blank scanning accuracy within ±0.3mm, and reduces the reference error of CNC machining.

Claims

1. A method for matching blank shapes in CNC machining of automobile molds, characterized in that: include: Step 1: Process the blank into a three-dimensional plane reference W, and perform a three-dimensional scan on the blank with W as the reference to obtain point cloud data of the blank's structure and surface; Step 2: Mesh the point cloud data of the part to be processed and use the envelope command of the software to obtain the minimum outer envelope unit of the point cloud data; Step 3, equally dividing the minimum outer envelope unit, specifically comprising: equally dividing the envelope into regular polyhedral units; the regular polyhedral unit is a regular tetrahedral unit or a regular hexahedral unit, whose side length is , , a is the average number of points in a single polyhedral unit cut; is the average density of the point cloud within the minimum outer envelope, , N is the total number of point cloud data of the processing installation surface; Step 4: Delete the noise point cloud data, specifically including: calculating the ratio of two adjacent polyhedral unit point clouds, the number of adjacent polyhedral unit point clouds is ,like , then delete the n point cloud data in the previous unit body, is a positive number less than 1, n, All are integers greater than 0; Step 5: Calculate the mean and standard deviation of the distance from the point cloud to the center point in the polyhedron unit, specifically including: if the coordinates of the center point of the polyhedron unit are , the number of point clouds in a single unit is b, and the distance from the point cloud to the center point is , ; The mean of the distance , the standard deviation of the distance ; Step 6: Determination and processing of point cloud data, specifically including: Determine whether the point cloud data meets the blank processing accuracy, k is the mold blank processing accuracy coefficient; if the calculated distance d from the point cloud to the center point within the volume unit does not meet the range, the point cloud data is deleted and marked in the digital model structure, and finally an STL data file is generated; Step 7: Compare and process the STL data with the design model, optimize and improve the machining program, and import it into the CNC machine tool program processing. After configuring the machine tool and tool according to the program, perform simulation inspection and simulation.

2. The method for matching the blank shape during CNC machining of automobile mold according to claim 1, characterized in that: The point cloud data of the surface structure of the male and female dies adopts tetrahedron elements, while the guide plate mounting surface, squat block, balance block, wedge drive seat, forming insert mounting surface and safety side pin processing surface structure adopt hexahedron elements.

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