The Geometric Error Identification And Compensation For Five-axis NC Machine Tools

This paper aimed at TH5656double rotary table five-axis NC machine tool, and the geometric error modeling, geometric error measuring and machining test are implemented. Based on the analysis of the motion relations among parts of the double rotary table five-axis NC machine tool, a geometric error model was established. The error compensation software was compiled and the NC machining code was compensated. Taking the impeller as example, machining verification experiments on error compensation model of machine tools were carried out. The main research contents are as follows:(1) The error model of the double rotary table five-axis NC machine tool was established. Based on the theory of multi-body system, topology structure of the double rotary table five-axis NC machine tool was analyzed. The coordinate tranform between ideal and actual movements of machine tool was presented completely with lower body array describing method. The geometric error model of five-axis NC machine tool was established, and this model is suitable for the maching tool with same struction.(2) The geometric error of translational axis and rotating axis was measured. Taking TH5656double rotary table five-axis NC machine tool as example, the geometric error measurement scheme on translational axis and rotating axis of the machine was designed. Twenty-one geometric errors of three translational axes were measured and identified by using laser interferometer instrument and digital level instrument, twelve geometric errors of two rotating axes were measured and identified by using ball bar.(3) An error compensation algorithm was proposed. On the basis of geometric error measurement and identification, a geometric error compensation model was established. Error compensation algorithm was proposed and error compensation program was compiled. The NC code was compensated with program offline.(4) Verification experiments on the error model of machine tool were carried out. Firstly, use ball bar to measure the error data of machine tool both before and after the error compensation. Through analyzing the comparison of the effect before and after the compensation, the effectiveness of the error compensation model was verified. Then, the impeller was machined with NC code before and after the compensation, and the profile errors of impeller blades were mesured. The effectiveness of the proposed method was proved with analysis.