Four-station laser tracer-based geometric error measurement of rotary table

Abstract

The geometric errors of numerical control (NC) rotary tables can be measured using a single instrument according to the conventional measurement method. This study presents an efficient method for this measurement using four-station laser tracers. A 3D coordinate measurement algorithm of the four-station laser tracer was established, the self-calibration of the laser tracer position and the spatial measuring point algorithm was realized, and the volumetric error of the measuring point on the rotary table was obtained. Then, the geometric errors of the NC rotary table were modeled using the screw theory, and a three-point measurement method was proposed to realize the separation of these geometric errors. Using the geometric error measurement experiment, six geometric errors of the NC rotary table were obtained. Compared with the conventional standard ball and laser interferometer measurement methods, the radial and axial runout results obtained using the laser tracer show differences of 0.08 and 0.07 µm, respectively, and the result of positioning error measurement shows a difference of 2.2 µrad. In addition, the method proposed in this study demonstrates an efficiency improved by five times, under the premise of ensuring the measurement accuracy, which broadens the possibilities for applications of rotation axes’ geometric error measurement in machining centers.