On the selection of flatness measurement points in coordinate measuring machine inspection

Inspection of form tolerances using the coordinate measuring machine (CMM) presents two distinct problems: data collection and data fitting. The former problem deals with the selection of the sample size and the sample point location while the latter involves the determination of the tolerance zone enveloping these points. Four types of strategies and five different sample sizes were studied in this work to address the former problem. The accuracy of flatness measurement was investigated using realtime experiments with respect to the above two factors and their respective levels. In addition, the length of the probe path was studied with respect to the two factors using a simulation study, A priority coefficient was developed to combine the influence of accuracy and path while selecting sampling strategies and sample size. Preliminary observations made suggest that any one sampling method may not be the best solution in all cases, while considering the accuracy of flatness and the shortest CMM probe path. (C) 1999 Elsevier Science Ltd. All rights reserved.