Design of a measurement system for measuring geometric errors of a workpiece table during two-axis synchronous motion

With the increasing customer demand for high-precision workpieces, the accuracy performance of CNC machine tools has become an increasingly important hot topic for almost all machine tool manufacturers. For fine surface finish workpieces, the performance of multi-axis synchronous motion has a significant impact on lathe processing. Accordingly, it is necessary to calibrate and identify the geometric errors of the workpiece table during multiple-axis synchronous motion. Therefore, this study proposes a novel noncontact optical measurement system for measuring the geometric errors of the workpiece table while the two axes are moving simultaneously. In addition, the horizontal CNC lathe machine iTC-2000LM, produced by Tongtai machine & tool Co., Ltd., was taken as the research vehicle. The proposed measurement system comprises an optics module composed of several reflectors, lenses, and cubic beam splitters; a sensing module composed of multiple two-dimensional position-sensitive detectors (PSDs); and a laser. Based on the principle of geometric optics theory and the optical triangulation method, complete mathematical models that describe the geometric errors of the workpiece table during two-axis synchronous motion were established using the skew-ray tracing method. Additionally, the essential features of the proposed measurement system were verified using the optical design software Zemax. Finally, a laboratory prototype system was constructed to experimentally verify the proposed measurement system. As mentioned above, the main contribution of this study is to design a novel and highly efficient measurement system with established measurement mathematical models and experimental verifications.