Accuracy and versatility of the NIST M48 coordinate measuring machine

Abstract

The NIST Is continuing to develop the ability to perform accurate, traceable measurements on a wide range of artifacts using a very precise, error-mapped coordinate measuring machine (CMM). The NIST M48 CMM has promised accuracy and versatility for many ears. Recently, these promises have been realized in a reliable, reproducible way for many types of 1D, 2D, and 3D engineering metrology artifacts. The versatility of the machine has permitted state-of-the-art, accurate measurements of one meter step gages and precision ball plates as well as 500 micrometer holes and small precision parts made of aluminum or glass. To accomplish this wide range of measurements the CMM has required extensive assessment of machine positioning and straightness errors, probe response, machine motion control and speed, environmental stability, and measurement procedures. The CMM has been used as an absolute instrument and as a very complicated comparator. The data collection techniques have been designed to acquire statistical information on the machine and probe performance and to evaluate and remove any potential thermal drift in the machine coordinate system during operation. This paper will present the data collection and measurement techniques used by NIST to achieve excellent measurement results for gage blocks, long end standards, step gages, ring and plug gages, small holes, ball plates, and angular artifacts. Comparison data with existing independent primary measuring instruments will also be presented to show agreement and correlation with those historical methods. Current plans for incorporating the CMM into existing measurement services, such as plain ring gages, large plug gages, and long end standards, will be presented along with other proposed development of this CMM.