Single-axis driven measurement method to identify position-dependent geometric errors of a rotary table using double ball bar

Abstract

With the development of error compensation technology, reliability and stability of error identification deserve much attention. And rotary axis errors of five-axis machine tool are the main error sources which result in machining inaccuracy. Hence, a new method for position-dependent geometric error (PDGE) identification of a rotary table using double ball bar was proposed in this paper. Especially, only the targeted rotary table was driven during the ball bar test, which can reduce the impact of interference error sources. During the measurement, the ball on the spindle holds still, and the ball on the rotary table rotates around the rotation axis. There are three mounting positions of magnetic socket on the rotary table. Total six measurement procedures of cone test are executed to obtain enough measuring results by setting different positions of magnetic socket ball. These measuring results are used to construct the identification model based on homogeneous transformation matrix (HTM). The impact of installation errors of the double ball bar on identified results was analyzed. The uncertainty of identified errors could be reduced with the single-axis driven and the installation parameter optimization. At last, testing experiments on a five-axis machine tool were conducted to verify the proposed method. The results confirm that the method is an effective way to identify PDGEs of a rotary axis, and the accuracy of identified results is improved.