Research On The Thermal Error Compensation Techniques Of Machining Center

Based on the analysis of the study status on the thermal error compensation techniques of CNC Machine tool, combined with the cooperation company requests, in order to work out the axial thermal error characteristics of Machining Center, to find the optimal temperature measuring point on spindle component, to establish a good thermal error compensation model through appropriate modeling method, then reduce the thermal error and increase machining precision, this paper research work have been done. The main contents are outlined as follows:At first, thermal error prevention and compensation methods on Machining Center are analyzed. The optical grating used on the Machining Center is detailed analyzed, not only compensate thermal error caused by screw-nut transmission, but also reduce the lead screw pitch error and reverse error, which greatly improves the position control precision on Machining Center. On the basis of this, the axial thermal error compensation as compensation degree of freedom is determined;Secondly, based on the analysis of heat transfer mechanism of spindle component on Machining Center, the steady-state heat transfer analysis and transient analysis of spindle component are analyzed by the finite element method, the spindle component temperature field distribution, from the non-equilibrium state to reach thermal equilibrium temperature curve and reach thermal equilibrium time are reached;Thirdly, use the heat transfer mechanism of spindle component analysis results, the various single-factor condition trials(13 trials), the constant speed, step speed, coolant temperature set and seasonal changes, are designed and detailed analyzed, the axial thermal error characteristics, the coolant temperature set specification and requirements of thermal compensation modeling test condition are obtained, proposed the concept of line density analysis between axial thermal error and temperature variable;Fourthly, on the basis of derived the axial thermal error characteristics and the existence of spindle optimum measuring point use heat transfer theoretical analysis, the layout of the spindle component temperature measuring points and trials are designed, through the correlation analysis and maximum residual error analysis obtain optimum measuring point region, integral residual error function and function fitting, the relatively accurate position of optimal temperature measuring point is derived from extreme value method, test verified the optimal measuring point thermal error compensation model has better accuracy. Get the general steps to obtain the optimal measuring point on spindle component through the test method;At last, based on the analysis of existing thermal error compensation modeling methods, real-time surplus temperature as independent variables, use multivariate linear regression modeling, which improves modeling accuracy and robustness; proposed to use multivariate linear regression modeling obtain thermal error compensation coefficients matrix, genetic algorithm optimize the compensation model coefficients, the maximum residual error minimum as objective function, get the balanced thermal error compensation model, increased the compensation modeling results.