Error sources in coordinate metrology: General considerations

In last four decades, the use of coordinate metrology increased, significantly, in all industry branches. Coordinate measuring machines (CMM) are versatile instruments, that facilitate general applications and reduce the time of the dimensional evaluations necessary to define the main characteristics of manufactured pieces. This way, they provide a much more modest metrological infrastructure, ideal for the integrated manufacture systems. However, of a metrological point of view, the more coveted properties of the coordinate measuring machine – its flexibility and versatility – turn them into extremely complex instruments when the goal is the evaluation of its volumetric performance and, even more, when its measurements traceability should be defined and the measurement uncertainty appropriately expressed. Since the beginning, the CMM volumetric performance has been studied by numerous institutions and research centers all over the world, as well as by the machines' manufacturers. In this work, the main sources of errors and uncertainties of coordinate measuring machines are presented and discussed, based on the results of a wide bibliographical search on the state of the art of coordinates measuring machines calibration and traceability.