A Study on the Secular Change of Three-Dimensional Coordinate Measuring Machines

One of the methods of improving the accuracy of the three-dimensional coordinate measuring machine (cmm) is numerical error correction. For the method, calibration of cmm must be carried out periodically. However, the long term stability of the accuracy cannot be predicted, and it is often difficult to determine the interval time of calibration. For the purpose of determining the periodic time of calibration, the secular change of a cmm has been investigated for over seven years. The same calibration procedure was performed with the cmm under the same environmental conditions. Results of tests show that the change in the accuracy occurs in a short period of one or two months. The accuracy must be frequently measured for the judgment of the time to practice the calibration procedure