Analysis And Optimization Of Thermal Characteristics Of HMC80 Horizontal Machining Center

High-speed and high-precision has been the development direction of precision machining center.With the research further it is difficult to reduce machining error by improving the static stiffness of machine tool system simply,because the thermal deformation caused by high-speed cutting occupies the main part of machining error.The thermal mechanical coupling is complicated in the machine tool,so it is necessary to establish a high-precision coupling model to study the temperature distribution and thermal deformation distribution of the machine tool,so as to optimize the model to meet the design requirements of high-speed and high-precision machine tools.In this paper,due to lack of study on the thermal mechanical characteristics of the interface in the whole model of the precision machining center,a finite element thermal-mechanical coupling model considering the thermo-mechanical parameters of important interface of HMC80 is established.Based on the FEA model,a structural optimization method is proposed to reduce machining error,the specific work carried out as follows:Firstly,build the rough surface model based on fractal theory and the Monte Carlo method.On the basis of the fractal contact theory the function of stiffness and thermal conductivity corresponding to contact gap and contact pressure of the important fixed interface are established.Secondly,the finite element thermo-mechanical coupling model of HMC80 is established,this model considers the thermal mechanical characteristics of interface.This article summarizes the heat generation calculation method of the bearing,motor,ball screw,guide and other components and calculation method of heat dissipation coefficient on different surfaces.The steady-state and transient temperature field and deformation field of the whole machine model are analyzed,then the accuracy of the model is verified by the comparison of the experimental results.The influence of thermal resistance of fixed interface on the temperature rise and effect of temperature on thermal deformation is studied.Finally,the thermal deformation law of the whole machine is studied by thermal error decomposition method.The structural optimization of the parts with large contribution to the machining error makes the thermal distortion of the tip point reduced by 12um.The parametric spindle and the spindle box model are established,the key optimization variables are extracted by parametric sensitivity analysis.The optimization model is constructed and the response surface optimization method is used to optimize the whole thermal error,as a result,the thermal distortion of the tip point of the model is reduced from 69.076um to 45.592um.