Reliability of Parameters for Associated Features in Coordinate Metrology.

In coordinate metrology, an associated feature (Gaussian associated feature) is normally calculated from a measured data set of CMM (Coordinate Measuring Machine) on a real feature using least squares method. Then, the associated feature is expressed without the geometrical deviation and the measuring uncertainty. However, the geometrical deviation and the uncertainty of the associated feature are key values to evaluate the function of machine parts. Therefore, the novel data processing method for evaluating the reliability of parameters for associated features has been developed. In this method, the reliability of each parameter of the associated feature can be processed from the standard deviation and the position of each measuring point using Jacobian matrix. Then, the uncertainties of parameters and deviations of the associated features can be calculated. This directly implies that these values and these calculations can be used for the evaluations of measurement uncertainties and a computational tolerancing.