Method for simultaneously measuring four-degree-of-freedom geometric errors of a rotary axis based on circular...

The rotary axis is a key component of high-end equipment such as multi-axis CNC machine tools, and its geometric errors have an extremely important impact on the processing, measurement, and control accuracy of the equipment. Current multi-degree-of-freedom (DOF) geometric error measurements methods for the rotary axis still face challenges such as complex decoupling, the necessity of servo rotation support, and the inability to achieve simultaneous and continuous full-cycle measurement with high precision. This paper proposes a novel method for simultaneously measuring the four-DOF geometric errors of the rotary axis based on a customized circular grating. This method requires no servo rotation support, is cost-effective, and boasts the advantages of simultaneous and continuous full-cycle measurement. Furthermore, its error-sensitive unit is small in size and light in weight, demonstrating the potential for embedded, rapid, and efficient measurement. We constructed a measurement device and conducted experiments. The repeatability values of the four-DOF rotary axis measurements were ±2.42 µm, 2.47 µm, ± 0.18 arcsec, and ±0.12 arcsec, respectively. The 1-hour stability standard deviations were 0.35 µm, 0.22 µm, 0.22 arcsec, and 0.16 arcsec, respectively. The results indicate that this method is effective, providing an approach for simultaneous and continuous full-cycle measurement of multi-DOF geometric errors of the rotary axis.