Thermo-structure Optimization Of NC Gear Milling Machine And Position Error Compensation

Sponsored by “Shanghai Municipal Commission of Economy and Informatization”, this paper focuses on the gear milling machine, YKHS2210 A, which is produced by Shanghai Pingxin Company, and studies its error mechanism, spindle thermo-structure optimization, positon and angular error modeling and error compensation.The main contents of this paper include the following aspects:(1) Based on the machining principle and movement mechanism of the CNC gear milling machine, a general synthetic error model is presented by using the theory of homogeneous coordinate transformation. According to the result of the general synthetic error model, this paper analyzes how the position error and angular error influence the accuracy of the gear milling machine and its product in detail, in order to provide theoretical foundation for structure optimization and error compensation.(2) Based on the analysis of the value of heat sources in the CNC gear milling machine when it works, its temperature filed and deformation filed are calculated by using the analysis of finite element. In this way, the structure of tool spindle is redesigned in order to decrease its thermal deformation and prevent from the influence of thermal error.(3) Because the accuracy of both feeding system and workpiece spindle system influence the accuracy of the CNC gear milling machine greatly, two different modeling strategies are offered for the position error and angular error. For the positon error, a compensation model based on the piecewise linear least squares fitting method is created in order to predict the positon error datum precisely. For the angular error, a compensation model based on trigonometric approximation theory is built in order to fit the angular error of the workpiece spindle precisely.(4) According to the study of KND K1000M4 II CNC system, a functional module for angular error compensation is developed. Then, position and angular error compensation tests is carried out. The accuracy of the gear milling machine and the tooth pitch error and its cumulative pitch error of a gear is measured and compared with the datum before compensation test. The results show that the accuracy of this gear milling machine is improved.