Effect of CMM point coordinate uncertainty on uncertainties in determination of circular features

Coordinate measuring machines (CMM) are commonly used to determine the parameters of a circular feature using different criteria like minimum zone, least squares, minimum circumscribed or maximum inscribed. For these criteria, the uncertainties in the evaluated parameters have been determined using Monte Carlo simulation. It has been assumed that the uncertainties in the point coordinates obtained from the CMM are independent, identical and normally distributed. The effect of varying CMM standard uncertainty on the mean and uncertainty interval width of all parameters has been shown graphically. The complete numerical results are provided for one case, which can serve as reference data. The results show that the nominal values of circularity error calculated from the measurement results may not represent the best estimates of the true value considering the measurement uncertainty.