Methods and Artifacts for Comparison of Scanning CMM Performance

Coordinate measuring machines (CMMs) with continuous-contact scanning capabilities are experiencing more and more use in a wide variety of discrete-part manufacturing industries. Many users of these CMMs, if asked, will say that their metrology requirements include high density scans at high speeds with high accuracy. These requirements are in conflict, as there will be some point at which the accuracy of the scanned data begins to decrease with an increase in the scanning speed. This paper addresses the effects of scanning speed on the performance of different CMMs using contact sensors. The use of a family of artifacts is proposed in order to evaluate the relative scanning performance as a function of scanning speed and the direction of the scan within the CMM volume. The artifacts that are developed for these tests have a sinusoidal waveform superimposed on a flat surface. This paper describes a series of experiments that utilize these artifacts and assess the ability of these tests to capture how a scanning CMM will perform when measuring actual parts.