Jun 08, 2020
Temperature has a great influence on parts with high requirements for grinding accuracy, and often the size of parts is excessive due to the difference between the grinding ambient temperature and the detection temperature of the inspection room. Especially for copper alloy materials with large expansion coefficients, this phenomenon is more obvious. In this paper, an effective method is proposed by grinding a certain type of part to solve the effect of temperature change on the accuracy of the part in non-ferrous metals.
Among the various factors that affect the accuracy of part grinding, the influence of temperature cannot be ignored, especially when grinding copper alloy materials, because the material has a large thermal expansion coefficient, temperature is the main reason that affects product quality. Often a batch of carefully processed parts has all passed the self-inspection dimensions. After the inspection, the temperature difference between the inspection room and the processing site is large, and the parts are subject to thermal expansion and contraction, which causes the batch inspection parts to be out of tolerance. After eliminating the influence of the temperature difference on the measurement, through multiple batch grinding of copper alloys, the results show that temperature is the key factor affecting the measurement accuracy of the part, and has been verified by the inspection results of the laboratory.
In this paper, a beryllium bronze part is taken as an example. The changes of the parts at two temperatures are compared and measured, and the corresponding grinding method is analyzed. The practice proves that this method is simple, reliable, practical and stable.
2 problems caused by grinding parts
After the parts have been ground, use a block gauge and a dial indicator to measure the parts.The on-site self-test value is significantly different from the test room's test value, ranging from 0.012 to 0.015 mm, and then returned to the site for review The dimensions are qualified again, and it is suspected that the operation and measurement errors affect the above phenomenon.
3 causes of problems
After analysis and thinking, the operation and measurement errors have a certain effect on the size, but the main reason is that when the parts are measured in two environments, the environmental temperature is greatly different, and the parts are subject to thermal expansion and contraction, especially in summer when the temperature is high. The temperature difference is greater.
4 Influence of temperature on part measurement
The temperature at the grinding site is significantly different from the temperature in the test room.The expansion coefficient of beryllium bronze is 1.78 × 10-5 / ℃. Changes at different temperatures are shown in Table 1.
It was determined that the site temperature of grinding a batch of parts was 28 ° C, the inspection room was 21 ° C, the first self-inspection was -0.002 mm, and the inspection room measurement was +0.015 mm. Serious impact.
1) Grind a piece with a fine grinding amount of 0.03 mm and send it to the inspection room for a fixed temperature of 0.5 h before measuring the part
2) Record the measured value at the measurement site with a marker according to the inspection results;
3) Take the recorded parts to the flat plate at the grinding site and set the temperature for 0.5 h;
4) Based on the data recorded by the part, the reprocessed part is compared with it to obtain the measured size, and grinding is performed according to the measured size.
According to this step, multiple batches of parts are processed and sent to the inspection room to measure and all meet the tolerance requirements. The results show that this method can effectively avoid the measurement errors caused by the different temperature and solve the key problems that affect the product quality.
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