Geometric Error Modeling And Compensation Research For CNC Gear Hobbing Machine

High-precision is an important tendency for modern CNC machine, CNC gear hobbing machine is gear cutting machine in many fields, and similarly owed the further demand for diagnosis correctness. based on error compensating technology compensated error for CNC machines,is the mainstream approach for study of error and improvement of accuracy to all of the country.In this paper, the compensation issue of geometric error for CNC gear hobbing machine,the analyzing and researching work is spread in several ways:(1) The geometric error is analysed for CNC gear hobbing machine.Starting from the principle of work for CNC gear hobbing machine, the respective sports into gear hobbing are analysed. On the basis of relative movement between hob and workpiece-radial direction、axial direction and tangent direction, the geometric error is analysed, geometric eccentric、motion eccentric and installation error of cutter are emphasis analysed, action principle of them and the influence on accuracy is expounded.(2)The geometric error model is founded for CNC gear hobbing machine. The geometric error model is founded based on the theory of multi-body system,firstly, the structure of CNC gear hobbing machine is analysed, the topological structure for CNC gear hobbing machine is acquired,then the topological structure is operated applying arithmetic of the lower body array, the lower body array for CNC gear hobbing machine is gained,next the movement relationship between adjacent bodys is researched,the characteristic matrix between adjacent bodys is got,at last these characteristic matrixs are computed according to the topological structure, the geometric error model of CNC gear hobbing machine is founded. Further, the geometric error model is decoupling based on the differential transformation method, the compensation quantity of separate axis is got.(3)The geometric error elements are measured and identified for CNC gear hobbing machine. The geometric error elements are divided into axis of movement and axis of rotation,twenty-one geometric error elements are measured and identified based on twelve line method appling laser interferometer, measuring line and identification principle of position error、pitching and deflection error、 verticality error and rolling error are analysed and expounded.Sixteen geometric error elements for CNC gear hobbing machine are measured and identified appling ballbar, measuring method and identification principle of parallelism error、axial runout error、radial run-out error、corner error and rotation error are analysed and expounded.(4)The compensating scheme of geometric error for CNC gear hobbing machine is designed. Three technology on error compensating are brief introduction,they are the method of modifying code off-line、the method of feedbacking interrupt and the method of translating origin,the computing method of the CNC instruments for the method of modifying code off-line is intensively expounded.At last combined with the structure for software and hardware of this numerical control system,the software flow of the compensating implementation of geometric error for CNC gear hobbing machine is raised.