Method for judging symmetry of discrete data points of profile curve of die stamping part

Abstract

The invention aims to provide a method for judging symmetry of discrete data points of a profile curve of a die stamping part, which comprises the following steps of: A, measuring by using a three-coordinate measuring instrument to obtain discrete data points of an outer profile of a stamping sample part, and sequentially measuring along the same hour hand direction; b, regarding all discrete data points on each section of curve as a set; c, for each set, ignoring z values of all discrete points, and respectively performing cyclic judgment to delete abnormal data to obtain a new set of data points; and D, for each new set, calculating an x-axis mean value and a y-axis mean value, recording the x-axis mean value and the y-axis mean value as the geometric center of the first section of curve, and then respectively carrying out the following judgment to obtain discrete data point symmetry judgment results of all the curves. According to the method, whether the discrete curve presents the point symmetry characteristic or not can be quickly judged, so that discrete point fitting can be quickly carried out, and reverse modeling of the discrete point curve and further reverse design of a mold are completed.

Description

Technical Field

[0001] The invention relates to the technical field of mold design, and in particular to a method for judging the symmetry of discrete data points of a mold stamping part contour curve. Background Art

[0002] Reverse design is a common method for mold design. The three-coordinate measurement of the sample is performed to collect its discrete data points. Then, through 3D software and corresponding algorithm recognition and curve fitting, the sample contour can be quickly and accurately modeled, laying the foundation for subsequent three-dimensional mold design.

[0003] It is worth noting that the shape of the sample may present a complex curve contour. The data collected by the three-coordinate system is a discrete data point set. How to use the algorithm to quickly identify the discrete curve data points and model the curve is a key core issue. Among them, the point symmetry judgment method for discrete curve data points is an important part, which is related to the accuracy of discrete point curve modeling, the accuracy of physical feature representation and the speed of curve modeling. Summary of the invention

[0004] The present invention aims to provide a method for judging the symmetry of discrete data points of a mold stamping part contour curve, which can quickly judge whether a discrete curve presents point symmetry characteristics, so as to quickly perform discrete point fitting, complete the reverse modeling of the discrete point curve and further reverse design of the mold.

[0005] The technical solution of the present invention is as follows:

[0006] The method for judging the symmetry of discrete data points of the mold stamping part contour curve comprises the following steps:

[0007] A. Use a three-coordinate measuring machine to measure and obtain discrete data points of the outer contour of the stamped sample, including the outermost edge curve and hole feature curve of the stamped part; when measuring, each hole feature or each outer contour edge is taken as a separate curve segment, and the discrete data points on the same curve segment are measured in the same clockwise direction;

[0008] B. Treat all discrete data points on each curve as a set, denoted by K i , i is the number of curve segments; the data points contained in each curve segment are represented by K ij (x ij ,y ij ) represents, j is the discrete point set of the curve;

[0009] C. For each set, ignore the z values ​​of all discrete points and perform cyclic judgments: rolling calculation of the geometric distance between each adjacent point. If the distance s1 between a point and its previous point and the distance s2 between a point and its next point are both greater than the preset threshold δ0, that is, s1>δ0 and s2>δ0, then the point is considered an abnormal point and deleted. The screening of abnormal data is completed to obtain a new set of data points K. ij ;

[0010] D. For each new set, for each segment of the data set, calculate the x-axis and y-axis mean K ij , denoted as the geometric center K of each curve i0 (x i0 ,y i0 ), and then make the following judgments respectively to obtain the symmetry judgment results of the discrete data points of all curves:

[0011] For any discrete point of the curve in the set, select any point as the starting point and set its coordinates as K i1 (x i1 ,y i1 )) is used as an active detection point, which is theoretically about the geometric center K of the curve segment. i0 (x i0 ,y i0 ) is symmetrical point: (x i1' ,y i1' )=(2x i0 -x i1 ,2y i0 -y i1 ); Determine whether there is a discrete point on this curve that is equal to (2x i0 -x i1 ,2y i0 -y i1 ) value coincides with the point, that is, the completely symmetrical point. If there is no point with (2x i0 -x i1 ,2y i0 -y i1 ) values, we use the traversal search method to further search and determine whether there is an approximately symmetrical point (x ij ,y ij );

[0012] If there is no completely symmetrical point or approximately symmetrical point, stop the next step of analysis and judgment, and directly evaluate the curve of the set as a non-point symmetrical curve; otherwise, search and judge the next point in a clockwise or counterclockwise order according to the discrete points until half of the total number of discrete points have completed the search and judgment; if all the search points of this section of the curve can find completely symmetrical points or approximately symmetrical points, then evaluate the contour curve of this section as a point symmetrical curve, otherwise evaluate the curve of this set as a non-point symmetrical curve.

[0013] In the step D, the theoretical symmetric point (x i1' ,y i1' ) is:

[0014]

[0015] Where n is the number of discrete points of the curve.

[0016] In the step D, the method for determining the approximate symmetric point is:

[0017] Traverse calculation (x ij ,y ij ) to (x i1' ,y i1' ) is the geometric distance, and the calculation formula is: D = ((x ij -x i1' ) 2 +(y ij -y i1' ) 2 ) 1 / 2 If the calculated geometric distance value is less than or equal to the preset threshold value δ1, that is, D≤δ1, it is considered that there is an approximately symmetrical point at the first detection point.

[0018] The threshold δ1 can be set as needed. The larger the δ1 is, the weaker the degree of strict point symmetry of the curve is. Conversely, the smaller the δ1 is, the stronger the degree of strict point symmetry of the curve is.

[0019] The present invention can make point symmetry judgment on discrete points of the stamping part contour curve, quickly perform curve fitting, complete reverse two-dimensional modeling of the discrete point curve and subsequent three-dimensional reverse design of the mold, and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the final result diagram of fitting the discrete data points of the stamping part according to the point-symmetric graph according to the method of Example 1. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0022] Example 1

[0023] The method for judging the symmetry of discrete data points of the contour curve of a die stamping part comprises the following steps:

[0024] A. Use a three-coordinate measuring machine to measure and obtain discrete data points of the outer contour of the stamped sample, including the outermost edge curve and hole feature curve of the stamped part; when measuring, each hole feature or each outer contour edge is taken as a separate curve segment, and the discrete data points on the same curve segment are measured in the same clockwise direction;

[0025] B. Treat all discrete data points on each curve as a set, denoted by K i , i is the number of curve segments; the data points contained in each curve segment are represented by K ij (x ij ,y ij ) represents, j is the discrete point set of the curve;

[0026] C. For each set, ignore the z values ​​of all discrete points and perform cyclic judgments: rolling calculation of the geometric distance between each adjacent point. If the distance s1 between a point and its previous point and the distance s2 between a point and its next point are both greater than the preset threshold δ0, that is, s1>δ0 and s2>δ0, then the point is considered an abnormal point and deleted. The screening of abnormal data is completed to obtain a new set of data points K. ij ;

[0027] D. For each new set, for each segment of the data set, calculate the x-axis and y-axis mean K ij , denoted as the geometric center K of each curve i0 (x i0 ,y i0 ), and then make the following judgments respectively to obtain the symmetry judgment results of the discrete data points of all curves:

[0028] For any discrete point of the curve in the set, select any point as the starting point and set its coordinates as K i1 (x i1 ,y i1 )) is used as an active detection point, which is theoretically about the geometric center K of the curve segment. i0 (x i0 ,y i0 ) is symmetrical point: (x i1' ,y i1' )=(2x i0 -x i1 ,2y i0 -y i1 ); Determine whether there is a discrete point on this curve that is equal to (2x i0 -x i1 ,2y i0 -y i1 ) value coincides with the point, that is, the completely symmetrical point. If there is no point with (2x i0 -x i1 ,2y i0 -y i1 ) values, we use the traversal search method to further search and determine whether there is an approximately symmetrical point (x ij ,y ij );

[0029] In the step D, the theoretical symmetric point (x i1' ,y i1' ) is:

[0030]

[0031] Where n is the number of discrete points of the curve.

[0032] The method for determining approximate symmetric points is:

[0033] Traverse calculation (x ij ,y ij ) to (x i1' ,y i1' ) is the geometric distance, and the calculation formula is: D = ((x ij -x i1' ) 2 +(y ij -y i1' ) 2 ) 1 / 2 If the calculated geometric distance value is less than or equal to the preset threshold value δ1, that is, D≤δ1, it is considered that there is an approximately symmetrical point at the first detection point.

[0034] If there is no completely symmetrical point or approximately symmetrical point, stop the next step of analysis and judgment, and directly evaluate the curve of the set as a non-point symmetrical curve; otherwise, search and judge the next point in a clockwise or counterclockwise order according to the discrete points until half of the total number of discrete points have completed the search and judgment; if all the search points of this section of the curve can find completely symmetrical points or approximately symmetrical points, then evaluate the contour curve of this section as a point symmetrical curve, otherwise evaluate the curve of this set as a non-point symmetrical curve.

[0035] Example 2

[0036] The three-coordinate measuring instrument is used to measure the discrete points of the stamping part contour. Under the premise of ignoring the height direction value, its plane coordinate value is extracted. The point symmetry judgment method of Example 1 of the present invention is used to automatically judge the symmetry of the collected data points. Therefore, when fitting the contour of the mold reverse design, the discrete points are fitted according to the point symmetry figure. The final result is shown in FIG. Figure 1 .

Claims

1. A method for judging the symmetry of discrete data points of a die stamping part contour curve, characterized in that: The following steps are involved: A. Use a three-coordinate measuring machine to measure and obtain discrete data points of the outer contour of the stamped sample, including the outermost edge curve and hole feature curve of the stamped part; when measuring, each hole feature or each outer contour edge is taken as a separate curve segment, and the discrete data points on the same curve segment are measured in the same clockwise direction; B. Treat all discrete data points on each curve as a set, denoted by K i , i is the number of curve segments; the data points contained in each curve segment are represented by K ij (x ij ,y ij ) represents, j is the discrete point set of the curve; C. For each set, ignore the z values ​​of all discrete points and perform cyclic judgments: rolling calculation of the geometric distance between each adjacent point. If the distance s1 between a point and its previous point and the distance s2 between a point and its next point are both greater than the preset threshold δ0, that is, s1>δ0 and s2>δ0, then the point is considered an abnormal point and deleted. The screening of abnormal data is completed to obtain a new set of data points K. ij ; D. For each new set, for each segment of the data set, calculate the x-axis and y-axis mean K i0 , denoted as the geometric center K of each segment i0 (x 10 ,y 10 ), and then make the following judgments respectively to obtain the symmetry judgment results of the discrete data points of all curves: For any discrete point of the curve in the set, select any point as the starting point and set its coordinates as K i1 (x i1 ,y i1 )) is used as an active detection point, which is theoretically about the geometric center K of the curve segment. i0 (x i0 ,y i0 ) is symmetrical point: (x i1' ,y i1' )=(2x i0 -x i1 ,2y i0 -y i1 ); Determine whether there is a discrete point on this curve that is equal to (2x i0 -x i1 ,2y i0 -y i1 ) value coincides with the point, that is, the completely symmetrical point. If there is no point with (2x i0 -x i1 ,2y i0 -y i1 ) values, we use the traversal search method to further search and determine whether there is an approximately symmetrical point (x ij ,y ij ); If there is no completely symmetrical point or approximately symmetrical point, stop the next step of analysis and judgment, and directly evaluate the curve of the set as a non-point symmetrical curve; otherwise, search and judge the next point in a clockwise or counterclockwise order according to the discrete points until half of the total number of discrete points have completed the search and judgment; if all the search points of this section of the curve can find completely symmetrical points or approximately symmetrical points, then evaluate the contour curve of this section as a point symmetrical curve, otherwise evaluate the curve of this set as a non-point symmetrical curve.

2. The method for determining the symmetry of discrete data points of a mold stamping part contour curve according to claim 1, characterized in that: In the step D, the theoretical symmetric points (x i1' ,y i1' ) is: Where n is the number of discrete points of the curve.

3. The method for determining the symmetry of discrete data points of a die stamping part contour curve according to claim 1, characterized in that: In the step D, the method for determining the approximate symmetric point is: Traverse calculation (x ij ,y ij ) to (x i1' ,y i1' ) is the geometric distance, and the calculation formula is: D = ((x ij -x i1' ) 2 +(y ij -y i1 ) 2 ) 1 / 2 If the calculated geometric distance value is less than or equal to the preset threshold value δ1, that is, D≤δ1, it is considered that there is an approximately symmetrical point at the measuring point.

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