Uncertainties in CMM Measurements, Control of ISO Specifications

In the scope of quality control, accurate evaluation of measurement uncertainties is a real challenge to improve the use of Coordinate Measuring Machines (CMM). In our work, a new method, based on a statistical approach of the problem, was therefore developed, to deduce instantaneous measurement uncertainties directly from the set of acquired coordinates. The covariance matrix of the intrinsic parameters which characterize each analyzed surface is also evaluated, thus allowing an accurate propagation of the measurement uncertainties to the ISO specifications to be controlled. The experiments carried out in our study illustrate this new statistical approach and demonstrate its relevance.