Calibration of rings using multi-step and reversal

This work concerns the application of multi-orientation techniques on CMMs for form error calibration of high accuracy workpieces. The form measurement capability of commercial CMMs is typically limited to some micrometer, e.g. for the inspection of roundness. The method presented herein deals with achieving sub-micrometer uncertainties in the calibration of rings on CMMs. The method is based on: i) systematic error separation using multi-step and reversal measurements, and ii) gaussian filtering of random errors. Validation of the method was provided through investigations on uncertainty contribution, implementation of the method on two different CMMs, and comparison using roundness testers. Measurements on a 100 mm diameter master ring with a form error of approximately 0.2 µm were carried out to illustrate the procedure. Measuring uncertainty better than 0.7 µm for diameter and 0.07 µm for roundness were achieved.