Evaluating the uncertainty of measurement in coordinate metrology is as important as it is difficult. It is important because the measurement results are used most often to make decisions about accepting or rejecting parts, and the associated risk is not under control without considering the uncertainty. It is difficult because coordinate measurements are all different (task‑specific uncertainty), no close‑form equations of the measurement exist and the error components (input quantities) are several hundreds and statistically correlated.
The EUCoM project attacked these problems with the objective of delivering two methods for the evaluation of the uncertainty suitable for use in industry and ready to offer the competent standardization body (ISO/TC 213/WG 10) for possible standardization. The first method is entirely experimental (a posteriori, type A according to the GUM) and does not require specific dimensional standard but a limited set of gauge blocks and a test sphere, likely available at most CMMs (Coordinate Measuring Machines). The second method is about prediction (a priori, type B) based on general information on the CMM (ISO 10360‑2 tests), also likely available. As the project developed, a second prediction method was developed, based on the same information.
The methods were validated experimentally in an extensive measurement campaign with industrial parts and dimensional standards, both in prismatic geometry and freeform, in discrete probing as well as in scanning mode. The results validated the method A and the very good prediction capability of the two methods B, even with the coarseness stemming from relying on mere general information about the CMM.
The ISO/TC 213/WG 10 has started the standardization project ISO 15530‑2, which intakes the method A, and is considering the methods B.
The INRIM initiated and coordinated the project. It contributed to all activities, and particularly to the method A.
Contributing scientific sectors
