Accuracy setting of measuring equipment

● minimum requirement: at present, the accuracy of CMM is generally required to be no more than 1 / 3 of the tolerance requirement of the tested product, which is the current minimum requirement. In other words, if the tolerance requirement of the product we want to measure is 0.03mm, the accuracy of CMM cannot be less than 0.01mm. ● MSA requirements: at present, many factories need to carry out MSA (measurement system analysis) to ensure that the measurement system meets the whole production process. In MSA, the specification requires that the accuracy of measuring instruments should not be greater than 1 / 10 of the tolerance requirements of the tested products. That is to say, if the tolerance of the product we want to measure is 0.03mm, the accuracy of CMM cannot be less than 0.003mm. Of course, this requirement is more stringent for some enterprises, and even can not be realized. For example, the processing accuracy of the slow wire device is about 0.003mm. If we choose the measuring equipment according to MSA regulations, we need the measuring equipment with the accuracy of 0.0003mm, which is very difficult to achieve. ● comprehensive consideration: when determining the accuracy of the measuring machine, we need to choose one of the above two situations, and more often, we need to choose a position between them to determine the accuracy. That is to say, if the precision we want to select is e and the product requires a tolerance of D, then 0.1D ≤ e ≤ 0.33d is OK.