A method for dimensional measurement of large tolerance small feature parts

Abstract

This application relates to the technical field of optical dimension measurement methods, and more specifically, to a dimension measurement method for small-feature parts with large tolerances. The method employs optical imaging to measure the dimensional features at intersection points. A relatively large error is allowed in the first measurement. Based on this, the intersection point is calculated as a first reference zero point. The feature elements are then measured again within the length range of the feature elements on both sides of the first reference zero point, and a second reference zero point is calculated. This process is repeated to obtain accurate feature element and intersection point dimensions. Using this measurement method, the problem of large measurement errors caused by poor consistency in the dimensional features at intersection points with large tolerances among different batches of parts is effectively solved, thus significantly improving the dimensional measurement accuracy of small-feature parts with large tolerances.

Description

Technical Field

[0001] This application relates to the field of optical measurement methods, and more specifically, to a method for measuring the dimensions of parts with large tolerances and small features. Background Technology

[0002] Optical measurement offers unique advantages over traditional coordinate measuring machines (CMMs), enabling rapid acquisition of actual points on a part's surface without contact, resulting in efficient and stable measurements. However, in practical measurement processes, there are special dimensional situations with large tolerances and small features, such as... Figure 2 As shown, the theoretical feature element R0.8 has a small measurable surface. During automatic measurement, the large variation in the length dimension (88.8) of different batches of parts within the tolerance range causes R0.8 to exceed the arc contour range during measurement, leading to significant errors in the intersection point dimension calculation. Similarly, for small feature dimensions with large tolerances, poor consistency in the length dimensions of different batches of parts can cause distortion in the measurement of small arcs of the feature element if the intersection point dimension of the part relative to the programmed part varies significantly during automatic measurement, resulting in large errors in the dimension calculation. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies in measuring small feature dimensions with large tolerances, and to provide a method for measuring the dimensions of small feature parts with large tolerances, which can effectively reduce the measurement error of small feature parts with large tolerances.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for dimensional measurement of small feature parts with large tolerances is provided, comprising the following steps: S1. Data Acquisition: Acquire images of the workpiece to be measured using an optical image measuring device, load the acquired images into the optical image measuring software, perform initialization preparation based on the operation method of the optical image measuring software, and set the standard model of the workpiece. S2. Initial acquisition of feature elements: Under the workpiece coordinate system, feature elements are selected and measured according to the image position. The selection of feature elements includes selecting line segments and arcs adjacent to the line segments respectively. S3. Obtain the first reference zero point: Construct the intersection point using the measured circular arc and measured straight line segment from step S2, and use it as the first reference zero point; S4. Determine the arc selection range: Determine the measurement selection range of the arc so that all acquisition points are located within the standard arc surface when measuring the arc; S5. First approximation measurement: Based on the first reference zero point and the arc selection range, select the straight line segment and the arc again and perform the measurement; S6. Obtain the latest reference zero point: Construct the intersection point of the previously measured arc and the measured straight line segment, and use it as the latest reference zero point; S7. Repeat approximation measurement: Based on the latest reference zero point and the arc selection range, select the straight line segment and the arc again and perform the measurement. Repeat steps S6 to S7 until all the acquisition points of the measured arc are within the standard arc surface range.

[0005] This invention provides a method for dimensional measurement of small-feature parts with large tolerances. It employs optical imaging to measure the dimensional features at intersection points. A relatively large error is allowed during the initial measurement. Based on this, the intersection point is calculated as a first reference zero point. The feature elements are then measured again within the length range of the feature elements on both sides of the first reference zero point, and a second reference zero point is calculated. This process is repeated to obtain accurate feature element and intersection point dimensions. Using this measurement method, the problem of large measurement errors caused by poor consistency in the dimensional measurements of small-feature parts with large tolerances across different batches of parts is effectively solved, significantly improving the dimensional measurement accuracy of such parts.

[0006] Furthermore, in step S3, the intersection point is constructed using the measured arc with error from step S2 and the straight line segment. One intersection point is obtained on each side of the center of the arc, and the intersection point between the measured straight line and the center of the arc is taken as the first reference point.

[0007] Furthermore, step S4 specifically includes: S41. Obtain the axial length value of the standard circular arc surface; S42. Determine the measurement range of the arc based on the axial length value obtained in step S41.

[0008] Furthermore, when determining the measurement selection range, the center of the selection range is located at the axial center of the arc, and the length of the selection range is less than the axial length.

[0009] Furthermore, in step S41, based on optical image measurement software, the axial length of the corresponding arc to be measured on the standard model of the workpiece to be measured is measured using the optical image measurement software through the constructed standard model of the workpiece to be measured.

[0010] Furthermore, when determining the length of the selection area, the length of the selection area is less than the axial length and not less than 90% of the axial length.

[0011] Furthermore, in step S6, the intersection point is constructed using the measured arc with error from the previous measurement and the straight line segment. One intersection point is obtained on each side of the center of the arc, and the intersection point between the measured straight line and the center of the arc is taken as the latest reference point.

[0012] Furthermore, in step S7, after all the acquisition points of the arc to be measured are within the range of the standard arc surface, the intersection point is reconstructed with the latest measured arc and the measured straight line segment. The intersection point between the straight line segment and the center of the arc is taken, and then the length from the intersection point to the reference surface is calculated to obtain the measured value of the arc.

[0013] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method described above.

[0014] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method described above.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a method for measuring the dimensions of parts with large tolerances and small features, which effectively solves the problem of large measurement errors caused by poor consistency of the dimensions of the intersection points of parts with large tolerances and small features in different batches, and effectively improves the measurement accuracy of parts with large tolerances and small features. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a dimensional measurement method for a small feature part with large tolerances in one embodiment. Figure 2 A schematic diagram of a workpiece with large tolerances and small feature dimensions; Figure 3 This is a schematic diagram of the first collection of surface elements in one embodiment; Figure 4 A schematic diagram of obtaining the first reference zero point in another embodiment; Figure 5 This is a schematic diagram illustrating the axial length of a standard circular arc surface obtained in one embodiment. Figure 6 This is a schematic diagram of the first approximation measurement in one embodiment; Figure 7 This is a schematic diagram of the approximation measurement after multiple repetitions in one embodiment. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0018] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0019] Example 1 This embodiment is a first embodiment of a dimensional measurement method for small feature parts with large tolerances. Because the length dimensions of small feature parts with large tolerances are inconsistent across different batches, if the intersection dimensions of the part relative to the programmed part vary significantly during automatic measurement, it can lead to distortion in the measurement of small arcs of the feature element, resulting in large errors in dimensional calculations. The measurement method provided in this embodiment, using optical imaging, involves selecting a bounding box on a surface at a specified location to collect actual points and fit the feature element. The bounding box position remains constant during measurement. For example, when the aforementioned length dimension is 88.80... +2 When the actual value varies within the tolerance range, selecting the arc may result in selecting outside the arc surface, such as... Figure 3 As shown, in this embodiment, a large error is allowed in the first measurement of small surface features; the intersection point can be constructed using the measured arc and straight line with a large error in the first measurement. At this time, two intersection points can be obtained, one located between the center of the straight line segment and the center of the arc (see attached diagram). Figure 3 (One is located to the left of the center of the circle), and the other is located on the other side of the center of the arc (attached). Figure 3 (To the right of the center of the circle), take the intersection point between the center of the straight line segment and the center of the arc as the boundary point and set it as the zero point (reference point). Select the straight line and the arc again to the left and right of this boundary point and calculate the intersection point. Repeat this approximation measurement to obtain accurate feature elements and then calculate the intersection point size.

[0020] like Figure 1 As shown in the figure, this embodiment provides a dimensional measurement method for small feature parts with large tolerances, which specifically includes the following steps: Step S1. Data Acquisition: Acquire images of the workpiece to be measured using an optical image measurement device, load the acquired images into the optical image measurement software, perform initialization preparation based on the operation method of the optical image measurement software, and set the standard model of the workpiece.

[0021] In this embodiment, both the optical measurement device and the optical image measurement software are commercially available. The detailed operating procedures vary depending on the specific device and software used, and adjustments can be made to adapt to the chosen device and software in practical applications. In this embodiment, Schneider Electric's Saphir measurement software is selected.

[0022] In step S1, the main purpose is to acquire an image of the workpiece to be measured and import the image into the measurement software, while establishing a standard model in the measurement software to facilitate calculation and comparison.

[0023] Step S2. Initial Acquisition of Feature Elements: In the workpiece coordinate system, feature elements are selected and measured according to the image position. Selecting feature elements includes selecting line segments and the arcs adjacent to the line segments. For example... Figure 3 As shown, the feature elements, straight lines and arcs, are selected based on the image location. However, when selecting the arc, the selection exceeds the arc surface range, resulting in a large measurement error.

[0024] Step S3. Obtain the first reference zero point: Construct the intersection point of the measured arc and the measured straight line segment in step S2, and use it as the first reference zero point.

[0025] In this step, the intersection point is constructed using the measured arc with error from step S2 and the adjacent straight line on the left. This will result in one intersection point on each side of the arc's center. The intersection point between the measured straight line segment and the arc's center is then taken as the first reference zero point, as shown in the attached figure. Figure 4 As shown.

[0026] Step S4. Determine the arc selection range: Determine the measurement selection range of the arc so that all acquisition points are located within the standard arc surface when measuring the arc.

[0027] To accurately measure a circular arc, all the actual selected data collection points need to be located within the arc surface and distributed over the largest possible area. Therefore, it is necessary to accurately determine the axial length of the arc surface. In this example, the axial length can be quickly obtained as 0.53 mm using a theoretical model. Figure 5 As shown.

[0028] To ensure that all sampling points are within the arc surface when measuring the arc, the center of the selected area should be located at the axial center of the arc segment, and the length of the selected area should be less than 0.53 mm and as large as possible. Therefore, in this embodiment, the length of the selected area is 0.51 mm.

[0029] Step S5. First approximation measurement: Based on the first reference zero point and the arc selection range, select the straight line segment and the arc again and perform the measurement.

[0030] like Figure 6As shown, a straight line is selected to the left of the first reference zero point, and a circular arc is selected to the right of the first reference zero point with a length of 0.51mm. It can be seen that the selected circular arc has significantly fewer sampling points outside the circular arc surface compared to the initially measured circular arc.

[0031] Step S6. Obtain the latest reference zero point: Construct the intersection point using the previously measured arc and straight line segment, and use it as the latest reference zero point. This step is similar in operation and principle to step S4.

[0032] Step S7. Repeat approximation measurement: Based on the latest reference zero point and the arc selection range, select the straight line segment and the arc again and perform measurement. Repeat steps S6 to S7 until all the acquisition points of the measured arc are within the standard arc surface range.

[0033] like Figure 7 As shown, similar to step S5, a measuring straight line is selected to the left of the latest reference zero point, and a measuring arc is selected to the right of it. Since the actual acquisition points of the selected arc no longer exceed the arc's surface range, the measured arc can be considered an accurate feature element. Then, the intersection point of the measured straight line and arc is constructed, and the length from the intersection point of the straight line segment and the arc's center to the reference plane is calculated to obtain the dimension 88.80. +2 The accurate measured value. In this embodiment, the reference surface is set according to the actual situation during measurement. In this embodiment, such as... Figure 2 As shown, this indicates the location pointed to by the left arrow.

[0034] This embodiment provides a method for dimensional measurement of small-feature parts with large tolerances. It employs optical imaging to measure the dimensional features at intersection points. A relatively large error is permissible in the first measurement. Based on this, the intersection point is calculated as a first reference zero point. The feature elements are then measured again within the length range of the feature elements on both sides of the first reference zero point, and a second reference zero point is calculated. This process is repeated to obtain accurate feature element and intersection point dimensions. Using this measurement method, the problem of large measurement errors caused by poor consistency in the dimensional measurements of small-feature parts with large tolerances across different batches of parts is effectively solved, significantly improving the dimensional measurement accuracy of such parts.

[0035] Example 2 This embodiment is an embodiment of a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method described in Embodiment 1.

[0036] Example 3 This embodiment is an embodiment of a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method described in Embodiment 1.

[0037] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0038] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the dimensions of small feature parts with large tolerances, characterized in that, Includes the following steps: S1. Data Acquisition: Acquire images of the workpiece to be measured using an optical image measuring device, load the acquired images into the optical image measuring software, perform initialization preparation based on the operation method of the optical image measuring software, and set the standard model of the workpiece. S2. Initial acquisition of feature elements: Under the workpiece coordinate system, feature elements are selected and measured according to the image position. The selection of feature elements includes selecting line segments and arcs adjacent to the line segments respectively. S3. Obtain the first reference zero point: Construct the intersection point using the measured circular arc and measured straight line segment from step S2, and use it as the first reference zero point; S4. Determine the arc selection range: Determine the measurement selection range of the arc so that all acquisition points are located within the standard arc surface when measuring the arc; S5. First approximation measurement: Based on the first reference zero point and the arc selection range, select the straight line segment and the arc again and perform the measurement; S6. Obtain the latest reference zero point: Construct the intersection point of the previously measured arc and the measured straight line segment, and use it as the latest reference zero point; S7. Repeat approximation measurement: Based on the latest reference zero point and the arc selection range, select the straight line segment and the arc again and perform the measurement. Repeat steps S6 to S7 until all the acquisition points of the measured arc are within the standard arc surface range.

2. The dimensional measurement method for parts with large tolerances and small features according to claim 1, characterized in that, In step S3, the intersection point is constructed using the measured arc with error from step S2 and the straight line segment. One intersection point is obtained on each side of the center of the arc, and the intersection point between the measured straight line and the center of the arc is taken as the first reference point.

3. The dimensional measurement method for parts with large tolerances and small features according to claim 1, characterized in that, Step S4 specifically includes: S41. Obtain the axial length value of the standard circular arc surface; S42. Determine the measurement range of the arc based on the axial length value obtained in step S41.

4. The dimensional measurement method for parts with large tolerances and small features according to claim 3, characterized in that, When determining the measurement selection range, ensure that the center of the selection range is located at the axial center of the arc, and that the length of the selection range is less than the axial length.

5. The dimensional measurement method for parts with large tolerances and small features according to claim 3, characterized in that, In step S41, based on optical image measurement software, the axial length of the corresponding arc to be measured on the standard model of the workpiece to be measured is measured using the optical image measurement software.

6. The dimensional measurement method for parts with large tolerances and small features according to claim 4, characterized in that, When determining the length of the selection area, the length of the selection area is less than the axial length and not less than 90% of the axial length.

7. The dimensional measurement method for parts with large tolerances and small features according to claim 1, characterized in that, In step S6, the intersection point is constructed using the measured arc with error from the previous measurement and the straight line segment. One intersection point is obtained on each side of the center of the arc, and the intersection point between the measured straight line and the center of the arc is taken as the latest reference point.

8. The dimensional measurement method for parts with large tolerances and small features according to claim 1, characterized in that, In step S7, after all the acquisition points of the arc to be measured are within the range of the standard arc surface, the intersection point is reconstructed with the latest measured arc and the measured straight line segment. The intersection point between the straight line segment and the center of the arc is taken, and then the length from the intersection point to the reference surface is calculated to obtain the measured value of the arc.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 8.

Images