On-line diagnostic tools for CMM performances

The on-line evaluation of the degradation of a coordinate measuring machine (CMM) performance, either due to variations of environmental factors, or to the deterioration of one of the CMM subsystems, is particularly important for the machine user. A sign of this interest is the large number of international standards that have been issued. The paper presents an approach for the on-line diagnostic of the metrological capabilities of a CMM. The method, which does not make use of additional internal or external instrumentation, is performed on-line during a normal measurement cycle. The graphical approach of the method, based on the use of control charts, permits a simple and immediate monitoring of the machine performance. Preliminary experimental results are presented and discussed.