Practicality and applications of body and face diagonal tests on machine tools

International standard ISO 230-6:2002 and American standard ASME B5.54-2005 (R2020) address body and face diagonal tests on machine tools and machining centres, respectively. ISO machine-specific standards do not include tests for checking machine performance when moving along diagonal trajectories across the full stroke of the axes. Consequently, there is no specified tolerance for these diagonal tests. This raises the need to investigate the applicability of these tests. ISO 230-6 highlights several potential uses for diagonal tests including “estimation of volumetric performance”, “acceptance tests” and “health check or reassurance” of machine tools. It also mentions that the results of face diagonal tests can be used to derive the mutual squareness of linear axes of the machine under test. This paper explores the potential applications of diagonal tests alongside their practicality in an industrial environment. Approximately 600 tests were conducted on a vertical machining centre with the kinematic chain of [w X’ Y’ b Z (C) t] at various trajectories with different angles within the machine’s working volume. Additionally, this paper explains how to select appropriate diagonal trajectory angles using Pythagorean triples and quadruples for ease of machine programming, convenient set up of laser software, and the elimination of rounding errors caused by NC algorithms or the machine’s encoders. Experimental results are compared with predicted outputs obtained by simulations based on the Homogeneous Transformation Matrices (HTM) method which is a robust technique for modelling volumetric errors of machine tools under rigid body assumptions.