A method for detecting a defective surface of a sheet metal part

Abstract

The application discloses a sheet metal part defect surface detection method, comprising the following steps: S1, a sheet metal part model is established through simulation and feature decomposition, and a set of surface basic units AFS is obtained; S2, upper and lower web surfaces A1 and A2 are determined; S3, a neighboring surface set AFS1 is obtained by neighboring surface screening on the surface basic unit set AFS, and a bending surface is screened out according to the neighboring surface set AFS1; S4, the bending surface obtained in S3 is uploaded to an experience database after compliance checking; S5, a bending surface set BFS is determined according to the bending surface in S3; S6, a sunken surface is determined according to the bending surface in the bending surface set BFS; and S7, the sunken surface obtained in S5 is uploaded to the experience database after compliance checking. i , according to the bending surface in the bending surface set BFS i , a sunken surface is determined; S6, the sunken surface obtained in S5 is uploaded to the experience database after compliance checking. The application can automatically identify the bending radius, bending thickness, sunken depth and sunken length of sheet metal parts, and perform compliance review on the detected bending surface and sunken surface through an experience formula. After the compliance checking is completed, the qualified data is uploaded to the experience database, the checking efficiency is improved, and the checking cost and error rate are reduced.

Description

Technical Field

[0001] This invention relates to a method for detecting defects on the surface of sheet metal parts, belonging to the field of sheet metal technology. Background Technology

[0002] With the rapid development of industries such as automobiles and shipbuilding, traditional design methods are gradually becoming obsolete and being phased out. Manufacturability analysis, as a concurrent engineering method, has emerged. Also known as manufacturability review, manufacturability analysis allows designers to assess the manufacturability of a product during the design phase using a range of tools and related knowledge bases. This ensures that the product meets manufacturing process requirements and possesses good manufacturability, while also guaranteeing its processing quality and functionality.

[0003] Inspection of defects in sheet metal parts is an important part of concurrent engineering, specifically the inspection of bending radii and depressions in curved surfaces. When bending sheet metal parts, excessively large bending radii can easily cause bending backlash, while excessively small radii can produce fine cracks or even breakage, thus affecting subsequent manufacturing and assembly processes.

[0004] Traditional inspection of bending radii and depressions requires manual identification and selection of the surfaces associated with the product's manufacturing information. However, for complex sheet metal parts, the number and distribution of bending and depression surfaces are numerous and complex. Traditional inspection methods are not only cumbersome and prone to oversights, but also inefficient and time-consuming. Summary of the Invention

[0005] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides a method for detecting defective surfaces of sheet metal parts. This invention filters out curved surfaces by identifying adjacent surfaces, and then filters out sunken surfaces by identifying curved surfaces. After the defective surface detection is completed, the data from both is uploaded to an experience database. This eliminates the need for manual identification, improves efficiency, simplifies operation, and reduces the error rate.

[0006] Technical solution: A method for detecting defects on the surface of sheet metal parts, comprising the following steps:

[0007] S1: Establish a sheet metal part model through simulation, and perform feature decomposition of the sheet metal part model into points, lines, and surfaces to obtain the set of basic surface elements AFS = {A1, A2, F}. i …}(i=1,2,3,…);

[0008] S2: Determine the upper web surface A1 and the lower web surface A2: Among all the outer surfaces of the sheet metal part, the upper web surface A1 has the largest area, and among all the inner surfaces of the sheet metal part, the lower web surface A2 has the largest area.

[0009] S3: Obtain the adjacent face set AFS1 by filtering adjacent faces through the basic unit set AFS, and then filter out the curved face according to the adjacent face set AFS1;

[0010] S4: After performing a compliance check on the curved surface obtained in S3, upload it to the experience database;

[0011] S5: Determine the bending surface set (BFS) based on the bending surface in S3. i According to the set of bending surfaces BFS i The bent surface in the middle determines the sunken surface;

[0012] S6: After performing a compliance check on the depression surface obtained in S5, upload it to the experience database.

[0013] This invention first establishes a sheet metal part model and performs feature decomposition of points, lines, and surfaces to obtain a set of basic surface units (AFS). Then, based on the area of ​​the outer and inner surfaces, the upper web surface (A1) and the lower web surface (A2) are determined respectively. Adjacent surfaces are then selected from the AFS to obtain an adjacent surface set (AFS1). Curved surfaces are then identified from the AFS1 set, and the bending surface set (BFS) is determined based on these curved surfaces. i Finally, based on the bending surface set BFS i The bending surface is used to determine the sunken surface. After the bending surface and sunken surface are checked for compliance, the qualified data is uploaded to the experience database. This makes it easier to provide a reference or directly call it when processing the same model of parts in the later stage. This improves the inspection efficiency, reduces the inspection cost and error rate. At the same time, the unqualified parameters can be recorded as detailed information of unqualified products as error experience values, which facilitates the data analysis and statistics of unqualified products in the later stage.

[0014] In the preferred embodiment, the specific steps of S3 are as follows:

[0015] S301: Adjacent face filtering: Remove the upper web face A1 and lower web face A2, faces that are not adjacent to the upper web face A1 and lower web face A2, and faces that are connected to both the upper web face A1 and lower web face A2 from the basic unit set of faces AFS, to obtain the adjacent face set AFS1.

[0016] S302: Curved Surface Filtering: Divide the adjacent surfaces in the adjacent surface set AFS1 into line contact surfaces and point contact surfaces, and denote them as sets AFS′ respectively. 11 and AFS' 12 For the line contact surface set AFS′ 11 and the point contact surface set AFS′ 12 Perform curved surface screening.

[0017] Preferably, the specific steps of adjacent face screening in S301 are as follows:

[0018] Remove the upper web surface A1 and the lower web surface A2 from the basic unit set AFS; based on the feature decomposition in S1, obtain the point and line features of the upper web surface A1 and the lower web surface A2 to determine the adjacent face F′ of the upper web surface A1 and the lower web surface A2. i This yields the initial neighbor set AFS′1={F′1,F′2,…,F′ i ,F′ i+1 ,F′ i+2}(i=1,2,3…) and remove faces F′ from AFS′1 that are not adjacent to the upper web face A1 and the lower web face A2. i+1 ;

[0019] Based on each neighbor F′ in the initial neighbor set i Determine the value of each adjacent face F′ i Does the corresponding set of adjacent faces {F″1, F″2, ...} contain the upper web face A1 and the lower web face A2, i.e., the adjacent face F′? i Does it connect both the upper web surface A1 and the lower web surface A2? If so, remove it from the initial adjacent face set AFS′1, and finally obtain the adjacent face set AFS1 = {F1, F2, ..., F}. t ,…,F i (1≤t≤i).

[0020] Preferably, in S302, the set of line contact surfaces AFS′ 11 The specific steps for screening curved surfaces are as follows:

[0021] The intersection lines of the line contact surface with the upper web surface A1 or the lower web surface A2 are discretized at equal intervals. At each discrete point, an isoparametric curve of the adjacent surface is constructed, and it is determined whether each isoparametric curve is a circular arc with a constant radius. If so, the angle α between the normal vector of the upper web surface A1 and the lower web surface A2 at the discrete point and the normal vector of the line contact surface is calculated, as shown in the following expression:

[0022]

[0023] Where n1 is the normal vector of the upper web surface A1 and the lower web surface A2, and n2 is the normal vector of the line contact surface;

[0024] Determine whether the included angle α at each discrete point is either 0° or 180°. If so, determine that the line contact surface is a curved surface, and use the line contact surface set AFS′. 11 After removing the non-curved surfaces, the set of curved surfaces of the line contact surfaces (AFS) is obtained. 11 .

[0025] Preferably, in S302, the point contact surface set AFS′ 12 The specific steps for screening curved surfaces are as follows:

[0026] The point contact surface F is obtained based on the feature decomposition in S1. t The line characteristics determine the point contact surface F t The adjacent faces {F″′1,F″′2,…}, combined with the set of curved surfaces AFS of the line contact surfaces obtained in S302. 11 Form a new set C = {F″′1, F″′2, ...} ∩ AFS 11 Determine the number of faces in set C. If set C contains only two faces, then the point contact surface is considered a curved surface. Then, use the point contact surface set AFS′. 12 After removing the non-curved surfaces, the set of curved surfaces at point contact points is obtained (AFS). 12 .

[0027] In the preferred embodiment, the specific steps of S4 are as follows:

[0028] Based on AFS (Advanced Surface Set) 11 and AFS 12 The intersection lines or intersection points of the curved surface with the upper web surface A1 and the lower web surface A2 are used to construct the isoparametric curve of the curved surface, and the radius R of the isoparametric curve is the bending radius of the curved surface; the bending thickness δ of the part is determined by the minimum distance between the upper web surface A1 and the lower web surface A2; the bending coefficient i and the correction coefficient c of the part that match the curved surface of the sheet metal part are obtained from the standard database.

[0029] Substitute the bending thickness δ, the bending coefficient i, and the correction coefficient c into the empirical formula to calculate the minimum bending radius R'. Determine whether the calculated minimum bending radius R' is less than the radius R of the constructed bending surface isoparametric curve, i.e., R' < R. If so, it is considered qualified, and the parameter value of the bending radius R is uploaded to the empirical database.

[0030] The empirical formula is:

[0031] R′=i·c·δ

[0032] Where i is the bending coefficient of the part, R is the bending radius of the part, R' is the minimum bending radius of the part, c is the correction coefficient of the part, and δ is the bending thickness.

[0033] In a preferred embodiment, the specific steps of S5 are as follows:

[0034] S501: Determine the set of bending surfaces BFS based on the bending surfaces in S3, and sort the bending surfaces in the set of bending surfaces BFS to obtain the set of continuous bending surfaces BFS. i ;

[0035] S502: By calculating the continuous bending surface set BFS i The angle β between the bent surfaces is used to determine the sunken surface.

[0036] In a preferred embodiment, the specific steps of S501 are as follows:

[0037] Based on the bending surfaces and their linear characteristics determined in S3, the adjacent surfaces of the bending surfaces are determined. After removing the bending surfaces and the upper web surface A1 and lower web surface A2, the set of bending surfaces is denoted as BFS = {BF1, BF2, ..., BF...}. t ,…,BF i}(i=1,2,…)(1≤t≤i);

[0038] Based on the bending surface BF t Line features for obtaining BF t Given the adjacent faces {BF′1, BF′2, ...}, and the set of bent faces BFS, form a new set D = {BF′1, BF′2, ...} ∩ BFS. Determine the number of faces in set D. If set D contains only one face, i.e., BF′1, BF′2, ... ... t If there is only one bent face among the adjacent faces, then the bent face BF will be... t Defined as boundary bending surface BF t+1 ;

[0039] The boundary bending surfaces BF in the bending surface set BFS t+1 Let BF be the starting face. t+1 Adjacent bending surfaces BF t+2 Then obtain the bending surface BF. t+2 Adjacent bending surfaces BF t+3 The bending surface sorting is completed until the next boundary bending surface appears. All surfaces from the starting surface to the next boundary bending surface are recorded as a continuous bending surface set (BFS). i .

[0040] In a preferred embodiment, the specific steps of S502 are as follows:

[0041] BFS for a set of continuous bending surfaces i All bent surfaces are screened to determine whether the bent surface is tangent to its adjacent bent surfaces. If the two adjacent bent surfaces are tangent to the bent surface, the bent surface is considered a transition surface. Using the boundary bent surface as the reference surface, the non-transition bent surfaces are judged as sunken surfaces. If the angle β between the non-transition bent surface and the reference surface is greater than 8°, the non-transition bent surface is considered a sunken surface.

[0042] In a preferred embodiment, the specific steps of S6 are as follows:

[0043] Extract the undercut length L and undercut thickness H based on the non-transition bent surfaces on both sides of the undercut surface; perform compliance check according to the empirical formula, highlight the undercut surface on the outer surface of the sheet metal part, determine whether the ratio of the undercut length L to the undercut thickness H is greater than or equal to the user-set or empirical data value a. If yes, it is determined to be qualified, and the parameter values of the qualified undercut length L and undercut thickness H are uploaded to the empirical database. The empirical formula is:

[0044] L / H≥a

[0045] where L is the undercut length, H is the undercut thickness, and a is a user-set or empirical data value.

[0046] Beneficial effects: The method of the present invention can automatically identify the bending radius, bending thickness, undercut depth and undercut length in sheet metal parts, perform compliance review on the detected bent surfaces and undercut surfaces through the empirical formula, and at the same time have the batch check function for a single or multiple parts of a given model; after the compliance check is completed, the qualified data is uploaded to the empirical database, which facilitates reference or direct invocation when processing parts of the same model in the later stage, improves the check efficiency, reduces the check cost and error rate, and at the same time, the unqualified parameters can be recorded as the detailed information of unqualified products, used as error empirical values, to facilitate data analysis and statistics of unqualified products in the later stage. Brief Description of the Drawings

[0047] To more clearly describe the technical solutions in the embodiments of the present invention or the prior art, the drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only the embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative efforts.

[0048] Figure 1 is the method flowchart of the present invention;

[0049] Figure 2 is the specific method flowchart of the present invention;

[0050] Figure 3 is a structural diagram of the sheet metal part of the present invention;

[0051] Figure 4 is a structural diagram of the sheet metal part of the present invention;

[0052] Figure 5 is a structural diagram of the sheet metal part of the present invention;

[0053] Figure 6 is a structural diagram of a single side of the sheet metal part of the present invention. Detailed Implementation Modes

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0057] like Figures 1-2 As shown, a method for detecting defects on the surface of sheet metal parts includes the following steps:

[0058] S1: Establish a sheet metal part model through simulation, and perform feature decomposition of the sheet metal part model into points, lines, and surfaces to obtain the set of basic surface elements AFS = {A1, A2, F}. i …}(i=1,2,3,…);

[0059] like Figures 3-5 As shown, in the embodiments of the present invention, topological decomposition is used for feature decomposition, and one side of the sheet metal part is inspected. The other sides are inspected using the same method as the one side. The set of surface elements is AFS = {A1, A2, F1, F2, ..., F...}. 30}

[0060] S2: Determine the upper web surface A1 and the lower web surface A2: Among all the outer surfaces of the sheet metal part, the upper web surface A1 has the largest area, and among all the inner surfaces of the sheet metal part, the lower web surface A2 has the largest area.

[0061] S3: Obtain the adjacent face set AFS1 by filtering adjacent faces through the basic unit set AFS, and then filter out the curved face according to the adjacent face set AFS1;

[0062] S301: Adjacent face filtering: Remove the upper web face A1 and the lower web face A2 from the face basic unit set AFS;

[0063] Based on the feature decomposition in S1, the point and line features of the upper web surface A1 and the lower web surface A2 are obtained, and the adjacent faces of the upper web surface A1 and the lower web surface A2 are determined to be {F1, F2, ..., F...}. 30}, from {F1, F2, ..., F 30 Remove the faces {F1, F2, F3, F4, F5, F...} that are not adjacent to the upper web face A1 and the lower web face A2. 13 ,F 16 ,F 17 ,F 18 ,F 19 ,F 20 ,F 21 ,F 27 ,F 28 ,F 29 ,F 30}, thus obtaining the initial neighbor set, AFS′1={F6,F7,F8,F9,F... 10 ,F 11 ,F 14 ,F 22 ,F 23 ,F 24 ,F 25 ,F 26},

[0064] Based on each neighbor F′ in the initial neighbor set i Determine the value of each adjacent face F′ i Does the corresponding set of adjacent faces {F″1, F″2, ...} contain the upper web face A1 and the lower web face A2, i.e., the adjacent face F′? i Does it connect both the upper web surface A1 and the lower web surface A2 at the same time? If so, remove it from the initial adjacent face set AFS′1.

[0065] That is, the set of adjacent faces of F6 is {A1, F1, F2, F7, F...} 14 ,F 15 ,F 16}, F 14 The set of adjacent faces is {A1, A2, F6, F...} 15 ,F 22}, F 12 The set of adjacent faces is {A1, A2, F5, F...} 10 ,F 11 ,F 13 ,F 21,F 26}, F 11 The set of adjacent faces is {A1, A2, F} 10 ,F 12 ,F 26}, F 15 The set of adjacent faces is {A1, A2, F1, F6, F...} 14 ,F 16 ,F 17 ,F 22}, due to F 14 F 12 F 15 and F 11 The adjacent face set of F contains both the upper web face A1 and the lower web face A2, therefore it can be determined that F 14 and F 11 Both of these surfaces simultaneously connect to the upper web surface A1 and the lower web surface A2, and should be removed from the initial adjacent face set AFS′1; the final adjacent face set is AFS1 = {F6, F7, F8, F9, F...}. 10 ,F 22 ,F 23 ,F 24 ,F 25 ,F 26};

[0066] S302: Curved Surface Filtering: Divide the adjacent surfaces in the adjacent surface set AFS1 into line contact surfaces and point contact surfaces, and denote them as sets AFS′ respectively. 11 and AFS' 12 For the line contact surface set AFS′ 11 and the point contact surface set AFS′ 12 Perform curved surface screening:

[0067] AFS′ of the line contact surface 11 Curved surface screening: The intersection lines of the line contact surface with the upper web surface A1 or the lower web surface A2 are diffused at equal intervals. At each discrete point, an isoparametric curve of the adjacent surface is constructed, and it is determined whether each isoparametric curve is a circular arc with a constant radius. If so, the angle α between the normal vector of the upper web surface A1 and the lower web surface A2 at the discrete point and the normal vector of the line contact surface is calculated. The expression is as follows:

[0068]

[0069] Where n1 is the normal vector of the upper web surface A1 and the lower web surface A2, and n2 is the normal vector of the line contact surface;

[0070] Determine whether the included angle α at each discrete point is either 0° or 180°. If so, determine that the line contact surface is a curved surface, and use the line contact surface set AFS′. 11 After removing the non-curved surfaces, the set of curved surfaces of the line contact surfaces (AFS) is obtained. 11={F6,F8,F9,F 10 ,F 22 ,F 24 ,F 25 ,F 26}

[0071] AFS′ of point contact surfaces 12 Curved surface screening: Point contact surface F is obtained based on feature decomposition in S1. t The line characteristics determine the point contact surface F t The adjacent faces {F″′1,F″′2,…}, combined with the set of curved surfaces AFS of the line contact surfaces obtained in S302. 11 Form a new set C = {F″′1, F″′2, ...} ∩ AFS 11 Determine the number of faces in set C. If set C contains only two faces, then the point contact surface is considered a curved surface. Then, use the point contact surface set AFS′. 12 After removing the non-curved surfaces, the set of curved surfaces at point contact points is obtained (AFS). 12 ={F7,F 23}

[0072] S4: After performing a compliance check on the curved surface obtained in S3, upload it to the experience database;

[0073] Based on AFS (Advanced Surface Set) 11 and AFS 12 The intersection lines or intersection points of the curved surface with the upper web surface A1 and the lower web surface A2 are used to construct the isoparametric curve of the curved surface, and the radius R of the isoparametric curve is the bending radius of the curved surface; the bending thickness δ of the part is determined by the minimum distance between the upper web surface A1 and the lower web surface A2; the bending coefficient i and the correction coefficient c of the part that match the curved surface of the sheet metal part are obtained from the standard database.

[0074] Substitute the bending thickness δ, the bending coefficient i, and the correction coefficient c into the empirical formula to calculate the minimum bending radius R'. Determine whether the calculated minimum bending radius R' is less than the radius R of the constructed bending surface isoparametric curve, i.e., R' < R. If so, it is considered qualified, and the parameter value of the bending radius R is uploaded to the empirical database.

[0075] The empirical formula is:

[0076] R′=i·c·δ

[0077] Where i is the bending coefficient of the part, R is the bending radius of the part, R' is the minimum bending radius of the part, c is the correction coefficient of the part, and δ is the bending thickness.

[0078] S5: Determine the bending surface set (BFS) based on the bending surface in S3. iAccording to the set of bending surfaces BFS i The bent surface in the middle determines the sunken surface;

[0079] S501: Determine the set of bending surfaces BFS based on the bending surfaces in S3, and sort the bending surfaces in the set of bending surfaces BFS to obtain the set of continuous bending surfaces BFS. i ;

[0080] Based on the bending surfaces and their linear characteristics determined in S3, the adjacent surfaces of the bending surfaces are determined. After removing the bending surfaces, the upper web surface A1, and the lower web surface A2, the set of bending surfaces is denoted as BFS = {F1, F2, F3, F4, F5, F6}. 17 ,F 18 ,F 19 ,F 20 ,F 21};

[0081] Based on the bending surface BF t Line features for obtaining BF t Given the adjacent faces {BF′1, BF′2, ...}, and the set of bent faces BFS, form a new set D = {BF′1, BF′2, ...} ∩ BFS. Determine the number of faces in set D. If set D contains only one face, i.e., BF′1, BF′2, ... ... t If there is only one bent face among the adjacent faces, then the bent face BF will be... t Defined as boundary bending surface BF t+1 ;

[0082] The boundary bending surfaces BF in the bending surface set BFS t+1 Let BF be the starting face. t+1 Adjacent bending surfaces BF t+2 Then obtain the bending surface BF. t+2 Adjacent bending surfaces BF t+3 The bending surface sorting is completed until the next boundary bending surface appears. All surfaces from the starting surface to the next boundary bending surface are recorded as a continuous bending surface set (BFS). i Taking the bending of one side of the sheet metal part as an example, BFS is divided into two sets of continuous bending surfaces, BFS1 and BFS2, i.e., BFS1 = {F 17 ,F 18 ,F 19 ,F 20 ,F 21};BFS2={F1,F2,F3,F4,F5}.

[0083] S502: By calculating the continuous bending surface set BFS i The angle β between the bent surfaces is used to determine the sunken surface.

[0084] like Figure 6as shown, perform surface screening on all bending surfaces in the continuous bending surface set BFS i , determine whether a curved surface is tangent to its adjacent bending surfaces; if the bending surfaces adjacent to both sides are tangent to the curved surface, the curved surface is regarded as a transition surface; taking the boundary bending surface as the reference surface, perform sunken surface judgment on non-transition bending surfaces, and if the included angle β between the non-transition bending surface and the reference surface is greater than 8°, the non-transition bending surface is considered as a sunken surface;

[0085] taking the bending on one side of the sheet metal part as an example, {F2}, {F4}, {F 18}, {F 20} are transition surfaces. Taking {F 17} as the reference surface of the BFS1 bending surface set, respectively calculate the included angles between {F 19}, {F 21} and the reference surface {F 17}, and judge whether they are sunken surfaces; taking {F1} as the reference surface of the BFS2 bending surface set, respectively calculate the included angles between {F3}, {F5} and the reference surface {F1}, and judge whether they are sunken surfaces.

[0086] S6: Perform compliance check on the sunken surfaces obtained in S5 and then upload them to the experience database:

[0087] as Figure 6 shown, extract the sunken length L and sunken thickness H based on the non-transition bending surfaces on both sides of the sunken surface; perform a compliance check according to the empirical formula, and highlight the sunken surface on the outer surface of the sheet metal part, judge whether the ratio of the sunken length L to the sunken thickness H is greater than or equal to the user-set or empirical data value a, if yes, it is determined to be qualified, and the parameter values of the sunken length L and sunken thickness H that pass the check are uploaded to the experience database, where the empirical formula is:

[0088] L / H≥a

[0089] where L is the sunken length, H is the sunken thickness, and a is the user-set or empirical data value.

[0090] The various embodiments in this specification are described in a progressive manner, each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively brief, and the relevant parts can be referred to the description of the method part.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting defects on the surface of sheet metal parts, characterized in that: Includes the following steps: S1: Establish a sheet metal part model through simulation, and decompose the sheet metal part model into points, lines, and surfaces to obtain a set of basic surface units. i = 1, 2, 3, ... S2: Determine the upper web surface and lower abdominal plate surface Of all the outer surfaces of a sheet metal part, the upper web surface has the largest area. Of all the inner surfaces of a sheet metal part, the lower web surface has the largest area. ; S3: Through the set of basic units opposite Neighbor face filtering yields the neighbor face set. According to the neighbor set Screen out curved surfaces; The specific steps of S3 are as follows: S301: Adjacent Face Filtering: Remove sets of face basic units upper web surface and lower abdominal plate surface , and the upper web surface and lower abdominal plate surface Non-adjacent faces and faces that are simultaneously connected to the web. and lower abdominal plate surface Given a face, obtain the set of adjacent faces. ; The specific steps of adjacent face screening in S301 are as follows: In the basic unit set of a surface Remove the upper web surface and lower abdominal plate surface The upper web surface is obtained based on the feature decomposition in S1. and lower abdominal plate surface The point and line features determine the upper web surface and lower abdominal plate surface adjacent The initial neighbor set is obtained. and from Middle removal and upper web surface and lower abdominal plate surface Non-adjacent faces ; Based on each neighbor in the initial neighbor set Determine each adjacent face Corresponding neighbor set Does it include the upper web surface? and lower abdominal plate surface That is, adjacent face Does it connect to the upper web surface at the same time? and lower abdominal plate surface If so, then start from the initial neighbor set. After removing from the middle, the final set of adjacent faces is obtained. ; S302: Curved Surface Filtering: Select adjacent face sets The adjacent faces in the equation are divided into line contact surfaces and point contact surfaces, and are denoted as sets respectively. and , for line contact surface set and point contact surface set Perform curved surface screening; The set of line contact surfaces in S302 The specific steps for screening curved surfaces are as follows: The line contact surface is aligned with the upper web surface. or lower abdominal plate surface The intersection lines are diverged at equal intervals. At each discrete point, isoparametric curves of adjacent surfaces are constructed, and it is determined whether each isoparametric curve is a circular arc of equal radius. If so, the upper web surface at the discrete point is calculated. and lower abdominal plate surface The angle between the normal vector and the normal vector of the line contact surface The expression is as follows: ； in Upper web surface and lower abdominal plate surface The normal vector, is the normal vector of the line contact surface; Determine the included angle at each discrete point Are all angles 0° or 180°? If so, then the line contact surface is determined to be a curved surface. (This is based on the set of line contact surfaces.) After removing the non-curved surfaces, the set of curved surfaces of the line contact surface is obtained. ; The point contact surface set in S302 The specific steps for screening curved surfaces are as follows: Point contact surfaces are obtained based on feature decomposition in S1. Line features determine point contact surfaces adjacent face Combined with the set of curved surfaces of the line contact surface obtained in S302 Form a new set Determine the number of faces in set C. If set C contains only two faces, then the point contact surface is considered a curved surface. After removing the non-curved surfaces, the set of curved surfaces of the point contact surfaces is obtained. ; S4: After performing a compliance check on the curved surface obtained in S3, upload it to the experience database; S5: Determine the set of bending surfaces based on the bending surfaces in S3. According to the set of bending surfaces The bent surface in the middle determines the sunken surface; The specific steps of S5 are as follows: S501: Determine the bending surface set BFS based on the bending surface in S3, and sort the bending surfaces in the bending surface set BFS to obtain the continuous bending surface set. ; The specific steps of S501 are as follows: Based on the curved surface and its linear characteristics determined in S3, identify the adjacent surfaces of the curved surface and discard the curved surface and the upper web surface. and lower abdominal plate surface Later, it was recorded as the set of bent surfaces. ; Based on the bending surface Line feature acquisition adjacent face Combined with bending surface set Form a new set Determine the number of faces in set D. If there is only one face in set D, then... If there is only one bent face among the adjacent faces, then the bent face will be... Defined as boundary bending surface ; Set the bending surfaces Boundary bending surface in Let this be the starting face, and obtain the value relative to the starting face. Adjacent bending surfaces Then obtain the bending surface. Adjacent bending surfaces The bending surface sorting is completed until the next boundary bending surface appears. All surfaces from the starting surface to the next boundary bending surface are recorded as a set of continuous bending surfaces. ; S502: By calculating the set of continuous bending surfaces The included angle of the bending surface in the middle Determine the sunken surface; The specific steps of S502 are as follows: For a set of continuous bending surfaces All bent surfaces are screened for surface curvature. It is determined whether a surface is tangent to its adjacent bent surfaces. If two adjacent bent surfaces are tangent to a surface, that surface is considered a transition surface. Using the boundary bent surface as a reference surface, non-transition bent surfaces are judged for depression. If the angle between a non-transition bent surface and the reference surface is... If the angle is greater than 8°, the non-transition bend surface is considered to be a sunken surface; S6: After performing a compliance check on the depression surface obtained in S5, upload it to the experience database.

2. The method for detecting defect surfaces of sheet metal parts according to claim 1, characterized in that: The specific steps of S4 are as follows: Based on curved surface set and The curved surface and the upper web surface and lower abdominal plate surface Based on the characteristics of the intersection lines or intersection points, construct the isoparametric curves of the curved surface, and the radius of the isoparametric curves is... That is, the bending radius of the curved surface; obtained from the upper web surface and lower abdominal plate surface The minimum distance between them determines the bending thickness of the part. Obtain the bending coefficient of the sheet metal part that matches the bending surface from the standard database. Part correction factor ; Bending thickness Part bending coefficient Part correction factor Substitute into the empirical formula to calculate the minimum bending radius Determine the calculated minimum bending radius. Is it smaller than the radius of the constructed curved surface or other parametric curve? ,Right now <R, if so, it is considered qualified, and the bending radius is set. The parameter values ​​are uploaded to the experience database; The empirical formula is: ； in The bending coefficient of the part. Let be the bending radius of the part. The minimum bending radius of the part. This is the correction factor for the part. The bending thickness.

3. The method for detecting defect surfaces of sheet metal parts according to claim 1, characterized in that: The specific steps of S6 are as follows: Extract the recess length based on the non-transition bent surfaces on both sides of the recessed surface , the recess thickness ; perform compliance check according to the empirical formula, and highlight the recessed surface on the outer surface of the sheet metal part, determine whether the ratio of the recess length and the recess thickness is greater than or equal to the user-set or empirical data value a. If yes, it is determined to be qualified, and the parameter values of the recess length that has passed the check , the recess thickness are uploaded to the empirical database, where the empirical formula is: ； in The length of the depression. For the thickness of the depression, Set or use user-defined data values.

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