Optimizing dynamic characteristics of NC rotary table based on electromechanical-hydraulic coupling

摘要

Dynamic characteristics of NC rotary table are a guarantee of indexing accuracy, which is composed of static indexing accuracy and dynamic indexing accuracy. Static indexing accuracy can be measured directly by laser interferometer, while dynamic indexing accuracy is too difficult to obtain directly because of load-carrying and work pattern of the table. To improve supporting rigidity and dynamic indexing accuracy of the NC rotary table, ZT20SW driven by a double worm gear pair was taken as the research subject. On the platform for gear milling, preload of the brake worm could be optimized by feedback of dynamic displacement on the working plane. On the basis of load analysis, an electromechanical-hydraulic coupling model in the circumferential direction of ZT20SW was established. Simulation and experiment results altogether indicated that preload on the brake worm could reduce the negative influences of backlash on dynamic characteristic. As a result, dynamic indexing accuracy of the table can be controlled reasonably and wear of the driving worm pair falls to minimum level. On the experiment platform of ZT20SW, frictional force was set to 600N by adjusting flow of the hydrostatic guideway. If preload reached 4400N, dynamic indexing accuracy of the table was less than 0.02mm.