Touch Probe Tip Compensation Using a Novel Transformation Algorithm for Coordinate Measurements of Curved Surfaces

A transformation algorithm compensating a radius of the probe tip and pre-travel errors is proposed to improve measurement uncertainty of a coordinate measuring machine (CMM). The transformation algorithm does not only compensate a radius of the probe tip, but it also compensates a slipping displacement from the predicted contact point caused by vertical tension for each data point. The performance of the transformation algorithm was successfully demonstrated by applying the transformation algorithm to raw data of an on-axis lens and an off-axis mirror measured with the CMM and comparing them with a reference data measured with UA3P-5 having several tens of nanometer accuracy.