Research on dynamic characteristics of NC rotary table considering leakage factors of its hydrostatic guideway

Abstract

The rigidity and damping characteristics of a large and heavy NC rotary table have great influence on machining efficiency and the integrated machine’s dynamic accuracy, but test and control methods related to these characteristics are difficult to apply. In the axial direction, the table was supported by a constant current hydrostatic guideway; the guideway’s surface roughness and planeness errors were the main factors contributing to hydraulic oil leakage. Based on the force analysis of a ZT20SW driven by double worm gear pairs, a dynamic model and an electromechanical–hydraulic coupling model in the circumferential direction were established. Simulation and experimental results altogether indicated that the cutting force on the table, leakage characteristics and Coulomb frictional force of the hydrostatic guideway each have great effects on dynamical accuracy. In addition, test methods on the leakage’s equivalent oil film thickness offer a new comprehensive evaluation standard for the hydrostatic guideway’s geometric errors. The hydrostatic guideway’s Coulomb frictional force can be controlled reasonably to improve the table’s dynamic accuracy.