Theoretical Analysis of Straightness Errors in Coordinate Measuring Machines (CMM) with Three Linear Axes

Diverse studies were developed in last years about the precision of coordinate measuring machines (CMMs) in order to enhance the calibration method for these testing devices or their application for dimensional verification of manufactured parts, but new research works are needed to identify the effect of the different types of geometric errors that exists in CMMs and deduce the measuring conditions that allow the optimization of CMM performance. The aim of this work consist of analyzing the influence of some of these machine errors such as the straightness errors and position errors associated to the CMM axis displacement, with the purpose of deducing the specific contribution of these errors inside the global uncertainty of these testing devices. This study was focused on coordinate measuring machines with a configuration type FXYZ, and it was carried out using a simplified model that is restricted to the effect of the straightness errors and position errors, without considering the contribution of the rest of CMM geometric errors. The unexpected variations that can be originated in the machine errors between the successive calibration points were described by the numerical model, and their influence on the CMM measuring accuracy were also discussed.