Evaluation of influence parameters on measurement reliability of coordinated measuring arms

Coordinate Measuring Arms (PCMAs or CMAs), despite using three-dimensional measurement techniques conceptually similar to the CMMs, are still manual measuring instruments for contact and their reliability requires an analysis of the most significant parameters of influence. In this work two types of tests were performed: in first place measurements of gauge blocks and ring gauges were made using the same CMA by several inspectors, thus simulating a study of repeatability and reproducibility (r&R). Based on preliminary results, a new study was carried out with more geometric features, over a "feature's master part" designed accordingly, and comparing the results with the measurements obtained in a CMM with traceability. This comparison has proven that measurement results are influenced not only by the operator (number and distribution of points, contact force, etc.) but also by the measured feature type and the probe type, thus by the CMA feasibility for measurement.