An evaluation method of contact measurement system of the coordinate measuring machine (CMM)

The purpose of this research is to present a method to evaluate the Coordinate Measuring Machine (CMM) measurement capability. The approach is based on contact measurement using block gauge and a factorial design technique. In this research, Repeatability and reproducibility are examined on a Gauge R&R, it address how precise a measurement system is. Furthermore, In order to capture accuracy of the system, we tackle the characteristics of bias, linearity and stability of the measurement system at the same time. According to the definition of length measurement by CMM, Time, block gauge and operator are the experimental factors and the response is the measuring value of block gauge by CMM. Because the time factor is not possible to randomize, so we use the time factor as block. In each block, use split-plot design to obtain the measuring value of block gauge. The result of the experiment showed that the accuracy and precision of length measure of CMM is remarkable. The bias, linearity, stability, and reproducibility of length measure of CMM can be accepted, repeatability estimation is extreme small, 0.1*10-7 inch2. The CMM in this experiment possesses enough measurement capability .The experimental method and analyzing process provided a concrete and feasible methodology to construct the assessment capability for CMM users, it also had extensive meaning and contribution for improving enterprise's ability in practice.