Comparison of Coordinate Measuring Machines using an Optomechanical Hole Plate

An interlaboratory comparison on mechanical and optical coordinate measuring machines (CMMs) was carried out in the period from August 2002 to November 2004. 15 different research laboratories were involved from 9 countries, with a total of 23 CMMs (12 mechanical and 11 optical) being used to measure an optomechanical hole plate, designed and manufactured by DTU, whereby it is possible to compare the performance of measurements obtained optically and mechanically. The comparison has shown that the optomechanical hole plate can be calibrated, following a well-established procedure for ball plate calibration, with uncertainties between 0.5 urn and 2 urn. Based on results from the comparison, optical CMM measurements can be divided in two groups. A group leading to deviations larger than 2 urn, and a group with deviations that are comparable to those obtained with mechanical machines. This comparison shows that optical coordinate measuring machines, generally speaking, can be as good as mechanical ones.