High-precision part machining method based on three-coordinate point cloud data

Abstract

The invention discloses a high-precision part machining method based on three-coordinate point cloud data, which comprises the following steps: selecting a probe according to the characteristics of a measured element of a part, establishing a workpiece coordinate system, measuring the part and storing a measurement result, if the measurement result is out of tolerance, establishing a new workpiece coordinate system, picking up one or more groups of point cloud data by using three-coordinate equipment, and machining the part according to the point cloud data. The corresponding coordinate values of all the points are analyzed, finally, the trimming position, trimming direction and trimming amount of the part are accurately obtained according to data comparative analysis of the coordinate values of all the points, and machining is conducted. By means of the method, the out-of-tolerance position of the part can be accurately judged, a processor is helped to accurately point out the trimming position, the trimming direction and the trimming amount, and the out-of-tolerance part can reach the qualified state after one-time repair.

Description

Technical Field

[0001] This invention relates to the field of mechanical engineering technology, specifically to a high-precision parts processing method based on three-coordinate point cloud data. Background Technology

[0002] When the form and position tolerances of high-precision parts exceed the tolerances, the machine operator often cannot accurately determine the direction and precise location of the deviation. This prevents the machine operator from making precise trimming, resulting in parts that are still unqualified after trimming. Sometimes, even after multiple trimmings, the parts are still unqualified, but there is no more room for trimming, ultimately leading to the scrapping of the parts.

[0003] Generally, after a part is measured by a coordinate measuring machine, the only results that can be obtained are the measured values ​​or out-of-tolerance values ​​of the part, but the specific out-of-tolerance location and direction cannot be given directly. Summary of the Invention

[0004] The purpose of this invention is to provide a high-precision part processing method based on three-coordinate point cloud data to overcome the above-mentioned technical defects.

[0005] The technical solution adopted by this invention to solve its technical problem is: a high-precision part processing method based on three-coordinate point cloud data, comprising the following steps:

[0006] Step 1: Place the high-precision part to be measured on the coordinate measuring machine (CMM) platform, select the appropriate probe according to the characteristics of the measured elements of the high-precision part, and complete the probe calibration.

[0007] Step 2: Establish the workpiece coordinate system using the coordinate system provided in the drawings or model;

[0008] Step 3: Compile a measurement program according to the drawing requirements, complete the part measurement, and save the measurement results;

[0009] Step 4: If the measurement results of the form and position tolerances of the part are out of tolerance, the measurement state of the high-precision part being measured on the marble platform should remain unchanged.

[0010] Step 5: On the original coordinate system of the measurement software, select one or more elements on the high-precision part being measured as reference directions to establish a new workpiece coordinate system according to the analysis needs.

[0011] Step 6: Based on the type of geometric tolerance to be analyzed, use a coordinate measuring machine to pick up one or more sets of point cloud data on the elements being analyzed on the part.

[0012] Step 7: In the newly created workpiece coordinate system, filter the coordinate values ​​of each axis of the collected points according to the analysis content, and directly or indirectly analyze the corresponding coordinate values ​​of each point according to the type of form and position tolerance to be analyzed.

[0013] Step 8: Based on the comparative analysis of the coordinate values ​​of each point, accurately determine the trimming position, trimming direction, and trimming amount of the part, and then proceed with the processing.

[0014] Furthermore, the high-precision parts in step one are shaft-type parts, pitch-type parts, or shell-type parts.

[0015] Furthermore, when the aforementioned form and position tolerance deviation is a coaxiality deviation, the method for determining the location of the deviation and the amount of trimming after the coaxiality deviation occurs is as follows:

[0016] First, select cylindrical surfaces A, B, and C at different positions on the part. The midpoints of the relative elements on their surface diameters all fall on the same reference center line. Define their common axis as the AB reference. Obtain the coaxiality of cylindrical surfaces A, B, and C relative to the AB reference. If cylindrical surface C exceeds the tolerance, combine its diameter and cylindricity to obtain its point cloud data in the workpiece coordinate system.

[0017] Then, the AB datum is used to determine the direction of a certain axis in X / Y / Z. The workpiece coordinate system is established with the AB datum as the X-axis, and the coordinate values ​​of cylindrical surface A and cylindrical surface B in the workpiece coordinate system are obtained.

[0018] Then, determine the deviation of cylindrical surface C relative to the Y-axis or Z-axis based on the Y and Z values ​​of the cylindrical surface C in the workpiece coordinate system;

[0019] Finally, according to the drawing requirements, the out-of-tolerance location and trimming amount between the measured element and the reference element are obtained.

[0020] Furthermore, when the aforementioned form and position tolerance deviation is an axial circular runout deviation, the method for determining the deviation location and trimming amount after the axial circular runout deviation occurs is as follows:

[0021] First, select two surfaces to be measured at different positions on the part, namely end face 1 and end face 2. Then measure the circles A and B corresponding to the two end faces respectively, define their common axis as AB datum, and obtain the axial circular runout of end face 1 and end face 2 relative to AB datum respectively. If end face 2 is out of tolerance, combine its flatness to obtain its point cloud data in the workpiece coordinate system.

[0022] Then, the AB datum is used to determine the direction of a certain axis in X / Y / Z. The workpiece coordinate system is established with the AB datum as the X-axis, and points 1, 2, 3, and 4 in the Z+ direction, Z- direction, and Y- direction are obtained on end face 1, and points 5, 6, 7, and 8 in the Z+ direction, Z- direction, and Y- direction are obtained on end face 2.

[0023] Finally, based on the distances from point 1 to point 5, point 2 to point 6, point 3 to point 7, and point 4 to point 8, the out-of-tolerance position and trimming amount between the measured element and the reference element are obtained.

[0024] Furthermore, the tilt direction of end face 2 can be analyzed by using the point data of the workpiece's three-coordinate system. By collecting data from several sets of points on end face 1 and end face 2, the trimming position can be confirmed more accurately.

[0025] The beneficial effects of this invention are: when a high-precision machined part has a form and position tolerance that exceeds the tolerance, the point cloud data of the coordinate measuring machine is used for analysis to accurately determine the position of the part that exceeds the tolerance. When the part has a reworkable allowance, it helps the machiner to accurately point out the trimming position, trimming direction and trimming amount. After using this patented method, the part that exceeds the tolerance can be made to meet the requirements after one rework. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view of the pitching component of the present invention;

[0027] Figure 2 This is a cross-sectional view of the shell-type part of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] When any part is subjected to coordinate measuring machine (CMM) measurement, all measured elements are recorded in the form of a point cloud. When the measurement results of a part are out of tolerance, the location, direction, and amount of the out-of-tolerance can be determined by analyzing the point cloud data of these measured elements.

[0030] This invention discloses a high-precision part processing method based on three-coordinate point cloud data, the steps of which are as follows.

[0031] Step 1: Place the high-precision part to be measured on the coordinate measuring machine (CMM) platform, select a suitable probe based on the characteristics of the measured elements of the high-precision part, and complete the probe calibration.

[0032] Step 2: Select the coordinate system given in the drawing or model to establish the workpiece coordinate system.

[0033] Step 3: Compile a measurement program according to the drawing requirements, complete the part measurement, and save the measurement results.

[0034] Step 4: If the measurement results of the part's form and position tolerances are out of tolerance, the measurement status of the high-precision part on the marble platform should be kept unchanged.

[0035] Step 5: On the original coordinate system of the measurement software, select one or more elements on the high-precision part being measured as reference directions to establish a new workpiece coordinate system according to the analysis needs.

[0036] Step 6: Based on the type of geometric tolerance to be analyzed, use a coordinate measuring machine to collect one or more sets of point cloud data on the elements to be analyzed on the part.

[0037] Step 7: In the newly created workpiece coordinate system, filter the coordinate values ​​of each axis of the collected points according to the analysis content, and directly or indirectly analyze the corresponding coordinate values ​​of each point according to the type of form and position tolerance to be analyzed.

[0038] Step 8: Based on the comparative analysis of the coordinate values ​​of each point, accurately determine the trimming position, trimming direction, and trimming amount of the part, and then proceed with the processing.

[0039] This invention retrieves point cloud data collected by a coordinate measuring machine (CMM) when measuring a workpiece, analyzes the point cloud information on the measured elements in the workpiece coordinate system, and accurately determines the positional relationship between the measured elements. This solves the problem that existing CMMs can only produce actual measurement results, but cannot accurately give the deviation position, deviation amount, and out-of-tolerance direction.

[0040] Analysis of coaxiality deviation.

[0041] Coaxiality is a form and position tolerance that frequently occurs during the machining process of parts, and it can occur in shaft parts, pitch parts, and housing parts.

[0042] When coaxiality exceeds the tolerance, the method for determining the location of the deviation and the amount of trimming is as follows: First, define coaxiality as the degree to which the axis of the measured cylindrical surface is not coaxial with the reference axis. If two cylinders or bodies of revolution are to be coaxial, the midpoints of the relative elements on their surface diameters must fall on the same reference center line.

[0043] like Figure 1 The pitch-type part shown has a coaxiality of cylindrical surface C relative to the common axis AB datum of 0.02. The result after coordinate measuring machine measurement is 0.0285, as shown in the table below.

[0044] .

[0045] The coaxiality deviation is 0.0085. The coordinates of the midpoints of the relative elements on the diameter of the cylindrical surface C can be analyzed according to the definition of coaxiality.

[0046] Before analysis, a workpiece coordinate system needs to be established. This workpiece coordinate system requires the AB axis to determine the direction of one of the X / Y / Z axes. This patent uses the AB axis to determine the direction of the X-axis. Therefore, the coordinates of circles A, B, and C are shown in the table below.

[0047] .

[0048] In the workpiece coordinate system with axis AB as the X-axis, Table 2 shows that the Y and Z coordinate values ​​of cylindrical surfaces A and B are both 0. The X-coordinate value is the distance between cylindrical surfaces A, B, and C, which is not considered here. In the coordinate values ​​of cylindrical surface C, the Y value is -0.002, and the Z value is -0.014. Therefore, it can be determined that cylindrical surface C deviates from axis AB mainly in the negative Z-axis direction by 0.014. To achieve a coaxiality of 0.02 for cylindrical surface C relative to axis AB during part rework, the center of cylindrical surface C needs to be moved between 0.004 and 0.024 along the Z-axis. Using this method, the following data was obtained after part rework: The Y coordinate value of cylindrical surface C is -0.0001, the Z value is 0.0075, and the coaxiality is 0.0151.

[0049] .

[0050] This method of analysis can accurately determine the precise position and direction of deviation between the measured element and the reference element. It provides precise trimming locations and amounts during part rework.

[0051] Analysis of excessive axial circular runout.

[0052] The axial circular runout (end face circular runout) tolerance zone controls the perpendicularity and shape error of the measured circumferential profile to the datum axis. For example... Figure 2 As shown.

[0053] The axial runout of end faces 1 and 2 relative to datum AB is no greater than 0.01 mm. However, the part inspection results are shown in the table below: the axial runout of end face 1 relative to datum AB is 0.007, and the flatness is 0.002. The axial runout of end face 2 relative to datum AB is 0.021, and the flatness is 0.003. The distance between the two end faces is 332.0550~332.0687 mm. Figure 2 It can be seen that end face 2 still has a trimming allowance of 0.13mm, therefore end face 2 needs to be reworked. The impact of flatness on the measurement results can be disregarded here. The next step is to determine how the runout of end face 2 exceeds the tolerance, that is, the positional state of end face 2 within this part.

[0054] .

[0055] Before analysis, a workpiece coordinate system needs to be established. The method for establishing the workpiece coordinate system was mentioned earlier when analyzing coaxiality; the same method can be used to establish the workpiece coordinate system when analyzing runout. After establishing the workpiece coordinate system, the tilt direction of end face 2 can be analyzed using the point data from the workpiece's three-coordinate system. Since the AB datum axis is the X-axis in the workpiece coordinate system, one point needs to be collected in each of the positive and negative directions of the Y-axis and Z-axis on end face 1, obtaining the data for points 1, 2, 3, and 4. Similarly, points 5, 6, 7, and 8 are collected at symmetrical positions on end face 2. The position coordinates of these eight points in the workpiece coordinate system are obtained, as shown in the table. Because the AB datum axis is now the X-axis, only the X-axis data is extracted when obtaining the coordinate data of each point; the Y-axis and Z-axis data are not relevant here.

[0056] .

[0057] By comparing the data at each point, it can be seen that the difference between the minimum and maximum values ​​on end face 1 is 0.007mm, and the value at point 3 is the largest. Therefore, it can be concluded that end face 1 is tilted by 0.007mm relative to the AB axis along the negative Z-axis, which is consistent with the runout error of end face 1. Observing the data at each point on end face 2, it is found that the value at point 7 has the largest deviation and is positive. To ensure that the end face runout is 0.01mm, the value at point 7 must be between 332.0502 and 332.0652. Therefore, the final conclusion is that 1 / 4 of the effective end face should be trimmed with point 7 as the center, with a trimming amount of 0.0107mm to 0.0257mm. After trimming the part using this method, the following data is obtained, as shown in the table below. The final axial circular runout of end face 2 relative to the AB datum is 0.008mm.

[0058] .

[0059] Based on this, collecting data from several more points on end face 1 and end face 2 can more accurately confirm the trimming position. In the example above, if end face 1 and end face 2 have parallelism requirements, this method can also be used for analysis, and the data at each point on end face 1 and end face 2 can be compared to obtain the data difference between corresponding points. Taking the data in the table above as an example, the following data is obtained as shown in the table below.

[0060] .

[0061] As can be seen from the table above, the maximum distance difference between end face 1 and end face 2 before repair was 0.0137 mm. Therefore, the parallelism of the two end faces was 0.0137 mm, and after repair, it was 0.0031 mm.

[0062] Those skilled in the art will readily understand that the above description is merely a preferred use case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision part machining method based on three-coordinate point cloud data, characterized by: The method comprises the following steps Step one, the measured high-precision parts are placed on a three-coordinate marble platform, appropriate measuring needles are selected according to the measured element characteristics of the high-precision parts, and the measuring needle calibration is completed; Step two, a coordinate system given by a drawing or a model is selected to establish a workpiece coordinate system; Step three, a measurement program is prepared according to the drawing requirements, the part measurement is completed, and the measurement results are saved; Step four, if the measurement results of the part shape and position tolerance appear to be out of tolerance, the measurement state of the measured high-precision part on the marble platform is kept unchanged; Step five, a certain element or multiple elements on the measured high-precision part are selected as reference directions to establish a new workpiece coordinate system on the original coordinate system of the measurement software; Step six, according to the type of the shape and position tolerance to be analyzed, one or more groups of point cloud data are collected on the analyzed element of the part by using the three-coordinate equipment; Step seven, according to the type of the shape and position tolerance to be analyzed, the coordinate values of the collected points are selected in the newly established workpiece coordinate system, and the corresponding coordinate values of the points are directly or indirectly analyzed according to the type of the shape and position tolerance to be analyzed; Step eight, according to the comparison and analysis of the coordinate values of the points, the trimming position, trimming direction and trimming amount of the part are accurately obtained, and the part is processed.

2. The high-precision part machining method based on three-coordinate point cloud data according to claim 1, characterized in that, The high-precision part in the step one is a shaft part, a pitch part or a shell part.

3. The high-precision part machining method based on three-coordinate point cloud data according to claim 2, characterized in that, When the shape and position tolerance is out of tolerance, the method for judging the out-of-tolerance position and trimming amount is as follows: Firstly, the measured cylindrical surfaces A, B and C are selected at different positions of the part, the midpoints of the relative elements on the surface diameters of the measured cylindrical surfaces A, B and C all fall on the same reference center line, the common axis is defined as the A-B reference, the coaxialities of the cylindrical surfaces A, B and C relative to the A-B reference are obtained, the cylindrical surface C appears out of tolerance, and the point cloud data of the cylindrical surface C in the workpiece coordinate system are obtained in combination with the diameter and the cylindricity of the cylindrical surface C; Then, the A-B reference is used to determine the direction of a certain axis in X / Y / Z, the workpiece coordinate system is established with the A-B reference as the X axis, and the coordinate values of the Y axis and the Z axis of the cylindrical surface A and the cylindrical surface B in the workpiece coordinate system are obtained; Then, the deviation of the cylindrical surface C relative to the Y axis or the Z axis is judged according to the Y value and the Z value of the cylindrical surface C in the workpiece coordinate system; Finally, the out-of-tolerance position and the trimming amount between the measured element and the reference element are obtained according to the drawing requirements.

4. The high-precision part machining method based on three-coordinate point cloud data according to claim 2, characterized in that, When the shape and position tolerance is out of tolerance, the method for judging the out-of-tolerance position and trimming amount is as follows: Firstly, two measured surfaces are selected as end surface 1 and end surface 2 at different positions of the part, and then the circles A and B corresponding to the two end surfaces are measured, the common axis is defined as the A-B reference, the axial circular runouts of the end surface 1 and the end surface 2 relative to the A-B reference are obtained, and if the end surface 2 appears out of tolerance, the point cloud data of the end surface 2 in the workpiece coordinate system are obtained in combination with the flatness of the end surface 2; Then, the A-B reference is used to determine the direction of a certain axis in X / Y / Z, the workpiece coordinate system is established with the A-B reference as the X axis, and the point 1 in the Z+ direction, the point 2 in the Y+ direction, the point 3 in the Z- direction, the point 4 in the Y- direction on the end surface 1, and the point 5 in the Z+ direction, the point 6 in the Y+ direction, the point 7 in the Z- direction and the point 8 in the Y- direction on the end surface 2 are obtained; Finally, according to the distance between point 1 and point 5, the distance between point 2 and point 6, the distance between point 3 and point 7, and the distance between point 4 and point 8, the overproof position and the cutting amount between the measured element and the reference element are obtained.

5. The high-precision part machining method based on three-coordinate point cloud data according to claim 4, characterized in that, The inclination direction of the end surface 2 is analyzed through the point position data of the workpiece coordinate system, and the cutting position is more accurately confirmed through the data of several groups of points collected in the end surface 1 and the end surface 2.

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