Theoretical Analysis of Circular Interpolation Contouring Error at Quadrant Changing Position in NC Machine Tools

This paper deals with the contouring errors of circular interpolation motion in NC machine tools. In order to analyze the errors at the quadrant changes, a dynamical model of a feed drive is proposed including the nonlinear spring characteristics of rolling ball guide way and the coulomb friction of a ballscrew and its support bearings. The generation of exponential-type lost motion and stick motion, which appears at quadrant change, is analyzed and those amounts at each angle of the circular motion are calculated by using this model. Several motion tests are conducted on a test stand, and the measured contouring errors coincide with calculation representing the dynamic behavior of the lost motion and stick motion.