Cage rivet hole position measurement method

In view of the small hole diameter of the rivet hole of the split cage of the deep groove ball bearing, the movement distance of the CMM probe in the hole is limited, and the hole position cannot be measured. The deviation correction method realizes the measurement of the position degree of the small aperture hole in the polar coordinate system, and the feasibility of the method is verified by an example. For the split-type semi-cage of deep groove ball bearings, the accuracy of riveting of the rivet holes determines the structural accuracy of the cage, thus affecting the bearing life. With the automation of processing equipment and the improvement of processing technology, the processing accuracy of rivet holes has also been improved. In order to verify the processing accuracy of rivet holes and provide measurement data to guide the processing process, it is necessary to measure the position of rivet holes. Usually, a three-coordinate measuring machine is used to measure the hole position. For a half cage with a rivet hole diameter less than 0.9mm, the hole position cannot be measured due to the limitation of the diameter of the three-coordinate probe and the moving distance of the probe in the hole. In order to solve the similar problem that the position degree of small-aperture holes cannot be measured, a three-dimensional optical measuring instrument is used for non-contact measurement, and the feasibility of the method is verified through experiments and data analysis. 1 Measuring principle The three-dimensional optical measuring instrument is a measuring instrument integrating optics, machinery, electronics, computer image processing and other technologies. It can measure the size, angle and position of various complex workpieces with high precision and high efficiency. 1.1 Measurement method and process Separation type half cage rivet holes are processed by outer diameter positioning and evenly distributed on the cage surface. 1.1.1 Roughly build the coordinate system Put the measured part on the appropriate position of the three-dimensional optical measuring instrument platform and fix it. Measure the reference circle according to the processing positioning method, move the lens to the center of the reference circle, clear the coordinates of the x, y, and z axes, and complete the workpiece positioning. 1.1.2 Measure a point on the reference circle in the precise coordinate system. According to the diameter of the reference circle, array this point 6 to 12 times and make it evenly cover the entire circumference. Automatically measure the remaining points and fit the measurement points to the reference circle. Select one of the rivet holes for automatic measurement, and construct the coordinate system x, y, and z axes with the obtained reference circle and rivet hole circle, and complete the precise construction of the coordinate system, as shown in Figure 1. Fig.1 Refined coordinate system1.1.3 Automatic measurement of rivet holes Measure one of the rivet holes, copy the measurement method of this hole, switch to polar coordinates and array this hole, the number of arrays is determined by the actual number of holes, and all rivets are automatically measured hole. 1.1.4 Evaluation of position degree Select one of the holes in the polar coordinate system, click the Nominal button, and the polar diameter and polar angle of the hole in polar coordinates will appear. Enter the theoretical value and tolerance into the corresponding table according to the requirements of the drawing, and use the polar angle and polar The diameter calculates the position degree. Follow this step to calculate the remaining hole positions in turn. 1.2 Data processing in the measurement process The rivet hole position degree measurement is calculated based on the deviation of the polar diameter and the polar angle. If one of the holes is used as the benchmark during measurement, the evaluation of the remaining hole position degree will cause the overall deviation from the nominal value. This is because the polar angles of all the holes deviate from the nominal value, and the holes are used as benchmarks for each other during the processing of the rivet holes of the split-type semi-cage, and it is not practical to use one of the holes as the benchmark for evaluation. Similarly, when measuring the positions of holes that are based on each other on a three-coordinate measuring machine, one of the holes cannot be used as a benchmark for evaluation. However, since each hole can move a certain angle in series, it can be evaluated by rotating the coordinate system. The principle of rotation Follow the 1/2 tolerance principle. However, the three-dimensional optical measuring instrument cannot rotate the coordinate system. After research, it is decided to use the polar angle correction method for evaluation. The correction parameter is 1/2 of the maximum polar angle deviation, as shown in Figure 2. Figure 2 Schematic diagram of polar angle deviation Fig. 2Diagram of polar angle deviation Assuming that the rivet hole of the split half cage is divided into 10 equal parts, the nominal value of the polar angle of the rivet hole is α=360°/10=36°. Assuming that the polar diameter and polar angle of each hole of the rivet hole after measurement are Di and βi respectively, then the polar angle deviation θi of each hole is the correction value of the polar angle deviation. δ is the conversion relationship between the rectangular coordinate system and the polar angle coordinate system. After the polar angle and polar diameter, the position degree φ is evaluated, that is, in the formula: r0 is the nominal value of the polar diameter. The position degree obtained according to the formula (3) is the actual required position degree, and the measured value can reflect whether the hole position degree is qualified and be used to guide the actual processing. 2 Test verification and result analysis The rivet hole diameter of a certain type of bearing half cage is 0.7 mm, divided into 14 equal parts, the nominal size of the center diameter is (41.9 ± 0.04) mm, and the positional degree is required to be 0.03 mm. From the uncorrected measurement results (Table 1), it can be seen that any hole is selected as the benchmark for evaluation, and the rest of the holes change with a certain regularity.