Method for automatically extracting and sequencing batch line features of three-dimensional thin-walled parts

Abstract

The invention provides a method for automatically extracting and sequencing batch line features of three-dimensional thin-walled workpieces, which comprises the following steps of: 1, importing a three-dimensional model of a thin-walled workpiece into off-line programming software, selecting a plurality of reference surfaces on a workpiece to be processed, automatically extracting all closed line sets on the selected reference surfaces, each closed line set serves as a candidate line feature, the candidate line features are screened according to the workpiece machining size requirement, and features to be machined are screened out; 2, acquiring a starting point of each screened to-be-processed line feature, setting a corresponding sorting parameter, and executing automatic sorting to obtain a plurality of sorted line features; and step 3, generating a processing track for processing a plurality of line features based on a track calculation function of the offline programming software. The method is high in calculation efficiency and can be widely applied to actual efficient machining of rotary parts and planar parts, and the machining efficiency of process scenes represented by laser cutting and quenching is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of three-dimensional thin-walled part contour processing, and in particular relates to a method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts. Background Art

[0002] Typical examples of three-dimensional thin-walled parts are metal stamping parts in the automotive parts industry, non-metallic interior and exterior decorations, and three-dimensional rotating shape crafts, which are mostly laser cut by multi-axis robotic arms or machine tools. The main feature of three-dimensional thin-walled parts is that the processing features are a large number of closed line features on the workpiece, which currently require manual selection and sorting, which is complicated to operate and difficult to sort.

[0003] In the existing three-dimensional model feature recognition and sorting scenarios, there is a lack of a comprehensive and universal closed contour recognition and sorting method. The invention patent "A circular hole feature recognition and processing method based on 3D model" with application number CN202211545665.1 proposes a circular hole feature recognition and processing method based on a 3D model, which searches and manages circular holes by hole processing process parameters, and generates processing trajectories for machine tools to clamp different tools for drilling or milling circular holes. Different from this, laser cutting of three-dimensional thin-walled parts uses the same tool to cut contours of different shapes, and its sorting method is based on a process that is mostly unrelated to the shape of the line features, but is related to the arrangement of the line features and the stability of the processing equipment. Therefore, the present invention intends to provide a high-efficiency and high-flexibility method for automatic extraction and sorting of batch line features of three-dimensional thin-walled parts. Summary of the invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for automatically extracting and sorting line features in batches of three-dimensional thin-walled parts, with the purpose of automatically and efficiently extracting and sorting line features in batches to replace tedious and complicated manual operations and improve the processing efficiency of three-dimensional thin-walled parts.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts, comprising the following steps: Step 1: Import the 3D model of the thin-walled workpiece into the offline programming software, select several reference surfaces on the workpiece to be processed, automatically extract all closed line sets on the selected reference surfaces, and use each closed line set as a candidate line feature. Screen the candidate line features according to the workpiece processing size requirements to select the features to be processed; Step 2: Get the starting point of each screened line feature to be processed, set the corresponding sorting parameters, perform automatic sorting, and obtain several sorted line features; Step 3: Generate a machining trajectory for machining several line features based on the trajectory calculation function of the offline programming software.

[0006] The offline programming software is the full-chain closed-loop CAM system software HiperMOS.

[0007] The automatic extraction method of candidate line features in step 1 is specifically as follows: selecting a processing area where the features to be processed are located in the three-dimensional model of a thin-walled workpiece as several reference surfaces on the workpiece, the several reference surfaces may be connected or discontinuous, and obtaining a closed line set composed of all boundary lines on all reference surfaces, each closed line set being a candidate line feature.

[0008] The specific method for screening the features to be processed in step 1 is as follows: In actual processing, not all closed contours need to be processed. The present invention proposes a screening method based on processing size requirements, constructing an OBB (oriented bounding box) for each candidate line feature, comparing the length, width and height of the OBB with the processing size, and screening out line features that meet the processing requirements as the features to be processed. The specific screening principle is: Assume that the three sides of the OBB are , the dimensions of the screening cube entered by the user are x-axis length a, y-axis length b, z-axis length c, assuming that the shortest edge in the OBB The corresponding axial direction corresponds to the Z direction of the screening cube, so the basis for the candidate features as the features to be processed is: ,in for The minimum value of for The maximum value of .

[0009] The sorting parameters in step 2 include the following three types: A. sorting object; B. sorting strategy; C. connection method.

[0010] In order to provide a feature sorting method for workpieces of various shapes and features, the three sorting parameters provided in step 2 are specifically: A. Sorting objects: supports three types of workpieces: spherical, cylindrical, and plane-like. Users can determine which of the three types of workpieces the workpiece is based on the specific shape of the workpiece to be processed.

[0011] B. Sorting strategy: Each type of workpiece provides 8 different sorting strategies: (1) horizontal ascending, vertical ascending; (2) horizontal ascending, vertical descending; (3) horizontal descending, vertical ascending; (4) horizontal descending, vertical descending; (5) vertical ascending, horizontal ascending; (6) vertical ascending, horizontal descending; (7) vertical descending, horizontal ascending; (8) vertical descending, horizontal descending. Users can decide which of the above eight sorting strategies to choose according to their processing needs.

[0012] The core of the automatic sorting algorithm in step 2 is to first extract the starting point of the feature as the sorting point, then map the sorting point to a two-dimensional parameter according to the type of the sorting object, then perform two-dimensional sorting according to the sorting strategy, and map the result of the two-dimensional sorting back to the sorting point to obtain the sorted line feature.

[0013] Taking a spheroid as an example, the sorting strategy (1) is explained as follows: First, establish a local coordinate system for the workpiece. For example, for a spheroid, the coordinate system is built at the center of the workpiece, with the positive z-axis as the North Pole axis, the horizontal direction representing the latitude parallel to the equator, and the vertical direction representing the longitude perpendicular to the equator. In the sorting strategy (1), the horizontal ascending order and the vertical ascending order result in connecting from the South Pole to the North Pole in a counterclockwise latitude direction.

[0014] C. Connection mode: Two connection modes are provided: unidirectional and reciprocating. Continuing with the above case, the connection mode is used to determine the connection mode between the first latitude and the second latitude. For example, unidirectional means that the two adjacent latitudes are both clockwise, and reciprocating means that the first one is clockwise and the second one is counterclockwise. Users can choose which connection mode to use according to actual working conditions.

[0015] The present invention has the following advantages: 1. The automatic batch extraction method and automatic sorting method of line features of thin-walled parts proposed in the present invention have high computational efficiency, can replace manual methods that are complex to operate and difficult to obtain reasonable results, and reduce time-consuming and labor-intensive manual operations.

[0016] 2. The automatic batching and sorting method of line features proposed in the present invention can be widely used in the actual efficient processing of rotating parts and planar parts, and can improve the processing efficiency of process scenarios represented by laser cutting and quenching. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the characteristics of a three-dimensional plane-like thin-walled part in an embodiment of the present invention; Figure 2 Schematic diagram of the characteristics of a three-dimensional spherical thin-walled flat part in an embodiment of the present invention; Figure 3 Schematic diagram of the characteristics of a three-dimensional cylindrical thin-walled part in an embodiment of the present invention; Figure 4 It is a schematic diagram of feature sorting for plane-like thin-walled parts; Figure 5 This is a schematic diagram of feature sorting for spherical thin-walled parts; Figure 6 Schematic diagram of feature sorting for cylindrical thin-walled parts. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further specifically described below through examples and in conjunction with the accompanying drawings. This embodiment provides three thin-walled parts of different shapes to illustrate the related feature automatic extraction and sorting methods, wherein Figure 1 It is a top view of a flat thin-walled part with several contours to be processed inside. Figure 2 This is a spherical decorative thin-walled part. The model is distributed with contours of various shapes to be processed. The solid line contour is seen from the front view, and the dotted line contour is the contour blocked from behind. Figure 3 It is a cylindrical thin-walled part with several circular contours to be processed distributed on its model.

[0019] Based on step 1 of the scheme of the present invention, a three-dimensional model of a thin-walled workpiece is imported, and several reference surfaces are selected on the workpiece to be processed, that is, the surfaces of the model introduced above, and all closed line sets on all reference surfaces can be automatically extracted according to the line-surface relationship and continuity. Each closed line set is used as a candidate line feature. In actual processing, not all closed contours need to be processed. For example, in the above three cases, only small contours need to be processed. The present invention proposes a screening method based on processing size requirements, constructs an OBB (a general algorithm in the field of computational geometry) for each candidate line feature, compares the length, width and height of the OBB of each candidate feature with the processing size requirements, and screens out line features that meet the processing requirements as features to be processed.

[0020] Step 2: Get the starting point of each line feature and select appropriate sorting parameters for sorting. Figure 1 , Figure 2 , Figure 3 The three thin-walled parts shown in the figure are used as examples to introduce the feature sorting method.

[0021] First, no matter it is a sphere-like, cylinder-like, or plane-like object, the general feature sorting steps are: calculate the two-dimensional parameters corresponding to the feature starting point, sort the two-dimensional parameters, and map to obtain the sorted features.

[0022] The following introduces the two-dimensional parameter calculation methods of three sorting objects: The class plane adopts the local coordinate system [ ] coordinates as two-dimensional parameters.

[0023] The spherical body is inversely solved using the spherical coordinate system to obtain the two-dimensional parameter selection. ], formula (1) is the spherical coordinates of this type of sphere, is the angle between the vector formed by a point on the sphere and the origin and the z-axis, is the angle between the projection vector of the vector formed by a point on the sphere and the origin on the XOY plane and the X-axis, is the radius of the sphere.

[0024] (1) The cylindrical coordinate system is used to inversely solve the two-dimensional parameters of the quasi-cylinder. ], is the angle between the vector formed by a point on the cylinder and the origin and the z-axis, is the z coordinate value of the point.

[0025] The sorting method based on two-dimensional points is as follows: first sort the first dimension parameters, then cluster, and then sort the second dimension parameters in each category. Based on the two-dimensional parameters, priority, and the positive and negative order of sorting, the present invention proposes 8 sorting strategies with different orders: (1) horizontal ascending order, vertical ascending order; (2) horizontal ascending order, vertical descending order; (3) horizontal descending order, vertical ascending order; (4) horizontal descending order, vertical descending order; (5) vertical ascending order, horizontal ascending order; (6) vertical ascending order, horizontal descending order; (7) vertical descending order, horizontal ascending order; (8) vertical descending order, horizontal descending order.

[0026] by Figure 4 Take the example to explain the sorting result of the plane-like sorting strategy (1) reciprocating connection: In the plane-like model, a local coordinate system is established so that the model is approximately parallel to the XOY plane, and the two-dimensional parameters are [ ], horizontal ascending means that the feature sorting result is parallel to the X-axis, and x is from small to large, and vertical ascending means that y is also sorted from small to large. In order to achieve this goal, first calculate the xy values ​​of all feature starting points, and then cluster all y values. As shown in the figure, the y values ​​are divided into 6 groups from small to large, and then x is sorted in each group. For example, the first group is from small to large. Due to the reciprocating connection, the x of the second group is arranged from large to small, and they are connected in sequence to form the feature sorting connection line shown by the dotted line in the figure.

[0027] by Figure 5 Take the spheroid sorting strategy (1) and the one-way connection as an example to explain the sorting results. The dotted arrows indicate the direction of the features after sorting: in the spheroid, the horizontal direction represents the latitude direction parallel to the equator, and the vertical direction represents the longitude direction perpendicular to the equator. In strategy 1, the horizontal ascending order means that the sorting is from bottom to top in the latitude direction, and the vertical descending order means that on each latitude line, the features are arranged counterclockwise. The one-way connection means that after the first circle of latitude lines, the second circle of latitude lines is still counterclockwise.

[0028] by Figure 6 Take the example of the cylinder-like sorting strategy (5) and the one-way connection sorting results: in the cylinder-like, the horizontal direction represents the direction perpendicular to the cylinder axis, and the vertical direction represents the direction parallel to the cylinder axis. In strategy 5, the vertical ascending order means that the sorting is the first dimension of the feature sorting extending in the counterclockwise direction parallel to the cylinder axis, and the horizontal descending order means that the second dimension parameter (z value) is arranged from large to small. One-way connection is a one-way connection between every two vertical arrangements.

[0029] The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope and spirit of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims

1. A method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts, characterized in that: The following steps are involved: Step 1: Import the 3D model of the thin-walled workpiece into the offline programming software, select several reference surfaces on the workpiece to be processed, automatically extract all closed line sets on the selected reference surfaces, and use each closed line set as a candidate line feature. Screen the candidate line features according to the workpiece processing size requirements to select the features to be processed; Step 2: Get the starting point of each screened line feature to be processed, set the corresponding sorting parameters, perform automatic sorting, and obtain several sorted line features; Step 3: Generate a machining trajectory for machining several line features based on the trajectory calculation function of the offline programming software.

2. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 1, characterized in that: The offline programming software is the full-chain closed-loop CAM system software HiperMOS.

3. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 1, characterized in that: The automatic extraction method of candidate line features in step 1 is specifically as follows: selecting a processing area where the features to be processed are located in the three-dimensional model of a thin-walled workpiece as several reference surfaces on the workpiece, wherein the several reference surfaces are connected or discontinuous, and obtaining a closed line set composed of all boundary lines on all reference surfaces, each of which is a candidate line feature.

4. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 1, characterized in that: The screening process of the features to be processed in step 1 is specifically as follows: constructing a directed bounding box (OBB) of each candidate line feature, comparing the length, width and height of the OBB with the processing size, and screening out line features that meet the processing requirements as the features to be processed.

5. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 4, characterized in that: The specific screening principle of the screening process is: Assume that the three sides of OBB are , the dimensions of the screening cube entered by the user are x-axis length a, y-axis length b, z-axis length c, assuming that the shortest edge in the OBB The corresponding axial direction corresponds to the Z direction of the screening cube, so the basis for the candidate features as the features to be processed is: ,in for The minimum value of for The maximum value of .

6. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 1, characterized in that: The sorting parameters in step 2 include the following three types: A. sorting object; B. sorting strategy; C. connection method.

7. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 6, characterized in that: The sorting objects include workpieces in three shapes: sphere-like, cylinder-like, and plane-like.

8. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 6, characterized in that: The sorting strategy includes 8 different order sorting strategies provided for each type of workpiece: (1) horizontal ascending order, vertical ascending order; (2) horizontal ascending order, vertical descending order; (3) horizontal descending order, vertical ascending order; (4) horizontal descending order, vertical descending order; (5) vertical ascending order, horizontal ascending order; (6) vertical ascending order, horizontal descending order; (7) vertical descending order, horizontal ascending order; (8) vertical descending order, horizontal descending order.

9. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 6, characterized in that: The connection modes include one-way connection and reciprocating connection.

10. The method for automatically extracting and sorting batch line features of three-dimensional thin-walled parts according to claim 1, characterized in that: The core of the automatic sorting algorithm in step 2 is to first extract the starting point of the feature as the sorting point, then map the sorting point to a two-dimensional parameter according to the type of the sorting object, then perform two-dimensional sorting according to the sorting strategy, and map the result of the two-dimensional sorting back to the sorting point to obtain the sorted line feature.

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