A method for obtaining gap surface difference through UG NX measuring points and simulating the matching of cross-sectional profiles

Abstract

The application discloses a kind of gap surface difference quasi-real matching measurement section profile methods for obtaining by UG measuring point, generate from UG measuring point to obtain the two-dimensional section profile required by gap surface difference quasi-real matching measurement of automobile assembly, specifically: first, according to the region of the required gap surface difference quality control in the CAD model of automobile assembly matching part, generate measuring point, determine gap surface difference measurement position and region according to measuring point and save in rectangular frame form.Finally, after the registration of the scanning point cloud of actual part and its corresponding CAD, the point cloud is sampled by the rectangular frame information obtained in the previous step, so that the two-dimensional section profile required by gap surface difference measurement is accurately obtained.

Description

Technical Field

[0001] This invention discloses a method for obtaining measurement information on the difference between measurement points and gap surfaces in UG NX, belonging to the field of geometric measurement technology. Background Technology

[0002] In industrial products, the vast majority of assemblies and subassemblies are assembled. The quality of assembly directly affects the quality of the product. For example, in passenger car door assembly, poor assembly can lead to problems such as poor airtightness, water leakage, and excessive wind noise. Another manifestation of assembly quality is the gap and surface difference between assembled parts. The magnitude of the deviation of gap characteristics and surface difference characteristics from their nominal values ​​is negatively correlated with assembly quality. Therefore, performing simulated matching on the model of parts before assembly can quickly verify the matching results, effectively reduce manufacturing adjustment costs, and accelerate the production process.

[0003] Currently, the measurement of gaps and surface differences in automotive assembly parts mainly relies on manual measurement by personnel using gap and surface difference rulers. This requires manual calibration of the spatial location for measuring the gaps and surface differences before measurement, which is repetitive and tedious, causing inconvenience. Using a simulated matching measurement method to mimic the actual matching process can quickly and efficiently obtain the gap and surface difference between matched parts. Simulated matching uses point clouds obtained from scanning actual parts for matching analysis. Before matching analysis, noise points in the point cloud are filtered out, and the reconstructed point cloud is registered with the corresponding CAD model.

[0004] Gap and surface difference measurement is based on a two-dimensional cross-section. When using simulated matching to measure gap and surface difference, it is necessary to obtain the two-dimensional profile of the cross-section. Therefore, determining the measurement location and region in the model has become an urgent technical problem to be solved. Summary of the Invention

[0005] This invention proposes a method for obtaining the cross-sectional profile of a simulated matching section for gap and surface difference measurement using UG NX measuring points. This method can obtain the two-dimensional cross-sectional profile required for simulated matching from UG NX measuring points, generate measuring points on the matching CAD model of the assembled parts, and then determine the measurement location area for gap and surface difference in the simulated matching using these measuring points. It is particularly applicable to the field of automotive parts assembly technology, enabling rapid verification of matching results, effectively reducing manufacturing adjustment costs, and accelerating the production process.

[0006] In accordance with the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for obtaining the cross-sectional profile of gap surface difference through UG NX measuring points is proposed. The method generates measuring points on the CAD standard models of a pair of matching parts, and the measuring points are distributed in pairs on the matching surfaces of a set of matching parts. The measuring points are used to determine the location and area where the gap surface difference needs to be measured, and the data is recorded and saved in the form of rectangular frames. After registering the scanned point cloud of the actual part with its corresponding CAD model, the point cloud is sampled using the rectangular frame information to obtain the two-dimensional cross-sectional profile required for gap surface difference measurement.

[0008] Preferably, a pair of matching parts is defined, consisting of a main part and related parts, wherein the main part is a reference part; the surface difference is the height difference between the upper surfaces of the two matching parts, and the gap is the assembly gap value between the two matching parts; and the two surfaces of the main part and related parts that are related to the measurement of the surface difference are defined as their respective surface difference matching surfaces, and the two surfaces that are related to the measurement of the gap are defined as their respective gap matching surfaces.

[0009] Preferably, UG NX measurement points are generated on the cross section where the gap surface difference needs to be controlled. Each cross section has 8 points, and the 8 points are located on the same plane. According to the principle of enclosedness, a rectangle is determined to exactly surround these 8 points.

[0010] More preferably, the measurement point generation rule is as follows:

[0011] The simulated gap difference measurement is based on the point cloud obtained by scanning the surface of the actual part. After filtering the point cloud, it is registered with its corresponding CAD model. By using a rectangular frame determined by scattering points, the point cloud is sampled within the rectangular frame area to obtain the two-dimensional cross-sectional profile required for the simulated gap difference measurement.

[0012] Preferably, for a pair of matching parts in the vehicle body assembly process, their matching surfaces are first obtained, and then eight measurement points are generated perpendicular to these matching surfaces. Based on the principle of containment, a rectangular area is determined to encompass these eight points. After processing the point cloud file and registering it with the CAD model, the spatial location and size of this rectangle are used to determine the measurement locations and areas required for virtual matching.

[0013] Compared with the prior art, the present invention has outstanding substantive features and significant advantages:

[0014] 1. This invention registers the scanned point cloud of the actual part with its corresponding CAD file, and then samples the point cloud to accurately obtain the two-dimensional cross-sectional profile required for gap and surface difference measurement. This enables rapid verification of the matching results, effectively reduces manufacturing adjustment costs, and accelerates the production process.

[0015] 2. The method of the present invention can quickly and efficiently obtain the gap surface difference between matching parts. After processing the noise information, the assembly accuracy of the parts is higher and the assembly verification process is more efficient. It is especially suitable for standardized parts assembly and final assembly production lines, improving and ensuring the working hours of industrial production, and ensuring a fast and efficient production process. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the principle of gap difference measurement in the method of the present invention.

[0017] Figure 2 This is a schematic diagram of UG NX measurement point generation on the CAD model of the method of the present invention.

[0018] Figure 3 This is a schematic diagram showing the registration of the CAD model and point cloud model of the method of the present invention.

[0019] Figure 4 This is a schematic diagram illustrating the method for obtaining the required spatial location information for simulated matching measurement using UG NX measuring points according to the present invention.

[0020] Figure 5 This is a schematic diagram illustrating the point cloud sampling range required for obtaining simulated matching measurements using UG NX measurement points in the method of this invention.

[0021] Figure 6 The method of this invention uses a rectangular sampling area to obtain a two-dimensional cross-sectional information map of the actual scanned point cloud of the part. Detailed Implementation

[0022] Example 1

[0023] In this embodiment, as Figure 1 and Figure 2 As shown, a method for obtaining the cross-sectional profile of a gap surface difference through UG NX measuring points is described. Measuring points are generated on the CAD standard models of a pair of matching parts, and these measuring points are distributed in pairs on the matching surfaces of a set of matching parts. The measuring points are used to determine the location and area where the gap surface difference needs to be measured, and the data is recorded and saved in the form of rectangular frames. After registering the scanned point cloud of the actual part with its corresponding CAD model, the point cloud is sampled using the rectangular frame information to obtain the two-dimensional cross-sectional profile required for gap surface difference measurement.

[0024] This embodiment utilizes the matching CAD model of the assembled parts to generate measurement points, and then uses these measurement points to determine the measurement location area for gap and surface difference in the simulated matching. It is suitable for applications in the field of parts assembly technology, enabling rapid verification of matching results, effectively reducing manufacturing adjustment costs, and accelerating the production process.

[0025] Example 2

[0026] This embodiment is basically the same as the previous embodiment, except that:

[0027] In this embodiment, Figure 1 This is a schematic diagram illustrating the principle of gap and surface difference measurement. The essence of gap and surface difference measurement is based on the measurement of a two-dimensional cross-sectional profile. In simulated matching measurement, the point cloud obtained from scanning the real part is filtered and then registered with a standard CAD model to reconstruct an STL model, such as... Figure 3 After obtaining the spatial planar position information of the measurement location, it is necessary to locally sample the STL model through this plane to obtain its two-dimensional contour information.

[0028] Using UG NX to generate measurement points, the feature lines of the matching group are used as the starting point. The status information of the lines is read, and the feature lines are cut and divided according to quality control requirements. A plane extending infinitely in space is created at the key positions after cutting. Then, the plane intersects with the surface difference matching surfaces and gap matching surfaces on the part to obtain the intersection line. Finally, attribute analysis is performed on the obtained intersection line to obtain 8 feature points: A1_end, A2_end, B1_end, B2_end, A1_begin, A2_begin, B1_begin, B2_begin, etc. Figure 4 As shown in the figure. A1_begin, A2_begin, B1_begin, and B2_begin are four points near the rounded corner, while A1_end, A2_end, B1_end, and B2_end are four points that are a specified distance before or after the four points near the rounded corner.

[0029] Given that determining the position of a spatial plane requires the coordinates of three points, find the unit normal to the plane by taking any three points from eight points. If we take A1_begin, A2_begin, B1_begin, and B2_begin and find the center point p(x0, y0, z0), then the plane can be represented as: A(x-x0)+B(y-y0)+C(z-z0)=0, where q(x, y, z) is a point on the plane.

[0030] After obtaining the planar information of the location to be measured, a rectangular sampling area is obtained with the center point p as the center and a specified distance. The sum of the normals of four points A1_end, A1_begin, B1_begin, and B1_end on the surface difference matching plane of the two parts is then used. The direction of the straight line containing the width of the rectangular sampling region; if the normals of these four points are respectively but The direction of the straight line on the other side of the rectangular sampling area

[0031] The center point p determines the location of the rectangle. and Having determined the orientation of the rectangle, the next step is to determine its size, i.e., its length and width.

[0032] Following the principle of inclusion, the sampling range rectangle is made to exactly circumscribing the four points A1_end, A2_end, B1_end, and B2_end. Let p be the set of these four points. i (i = 1, 2, 3, 4) then the length of the rectangular sampling region In the formula For p i The vector formed by the center point p is the width of the rectangular sampling region.

[0033] like Figure 5 As shown. Next, during the simulated matching measurement, the rectangular cross-sectional frame obtained from the scattered points is used to sample the reconstructed STL model to obtain the two-dimensional contour information at that location, as shown below. Figure 6 The gap difference size is obtained by processing the two-dimensional contour information using a specific gap difference algorithm.

[0034] This embodiment describes a method for generating UG NX measurement points to obtain the two-dimensional cross-sectional profile required for the simulated matching measurement of gap and surface difference in automotive assembly. First, measurement points are generated in the CAD model of the automotive assembly matching part according to the area requiring gap and surface difference quality control. The measurement location and area for gap and surface difference are determined based on these measurement points and saved as rectangular frames. Finally, after registering the scanned point cloud of the actual part with its corresponding CAD model, the point cloud is sampled using the rectangular frame information obtained in the previous step, thereby accurately obtaining the two-dimensional cross-sectional profile required for gap and surface difference measurement.

[0035] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for obtaining gap surface difference simulation matching measurement cross-sectional profile through UG NX measuring points, characterized in that: On the mating surfaces of the standard CAD models of a pair of matching parts, measurement points are generated in pairs. For each measurement section, eight coplanar feature points are generated, including four basic measurement points located at the fillets (A1_begin, A2_begin, B1_begin, B2_begin) and four endpoints located at specified distances before or after the basic measurement points (A1_end, A2_end, B1_end, B2_end). The locations and areas requiring gap / surface difference measurement are determined using these measurement points, and a rectangular frame is generated and saved using the following steps: (1) Calculate the center point of the measuring rectangle from the coordinates of the four basic measuring points. and the unit normal vector of the plane ; (2) Calculate the width direction vector of the rectangular frame from the sum of the normals of the four measuring points on the surface difference matching surface. ; (3) From the width direction vector and unit normal vector The cross product yields the length and direction vector of the rectangle. ; (4) According to the principle of inclusion, make the rectangle exactly circumscribed by the four endpoints, and project the lines connecting the four endpoints to the center point onto the length direction vector and the width direction vector respectively. Take twice the maximum projection value as the precise length and width of the rectangle. After registering the scanned point cloud of the actual part with its corresponding CAD model, the point cloud is sampled using the rectangular frame information to obtain the two-dimensional cross-sectional profile required for gap and surface difference measurement.

2. The method for obtaining gap surface difference simulation matching measurement section profile through UG NX measuring points according to claim 1, characterized in that: Define a pair of matching parts, divided into a reference part and a related part; the surface difference is the height difference between the upper surfaces of the two matching parts, and the gap is the assembly gap value between the two matching parts; the surface difference matching surface is the surface that generates the basic measuring points A1_begin, B1_begin and endpoints A1_end, B1_end, and the gap matching surface is the surface that generates the basic measuring points A2_begin, B2_begin and endpoints A2_end, B2_end; the width direction vector of the rectangular sampling area is determined by the sum of the normals of the four measuring points on the surface difference matching surface; the width direction is consistent with the reference direction of the surface difference measurement to ensure that the surface difference calculation result is comparable to the nominal value.

3. The method for obtaining gap surface difference simulation matching measurement section profile through UG NX measuring points according to claim 1, characterized in that: The eight feature points are strictly located in the same measurement plane, and the generated rectangle is circumscribed by four endpoints and includes all four basic measurement points.

4. The method for obtaining gap surface difference simulation matching measurement section profile through UG NX measuring points according to claim 1, characterized in that: After filtering the point cloud obtained from scanning the actual part surface, it is registered with its corresponding CAD model. Then, the point cloud is sampled within the rectangular frame generated by the above measurement points to obtain the two-dimensional cross-sectional profile required for the simulated gap surface difference measurement.

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