Research On Thermal Characteristics And Thermal Error Prediction Of Trunnion Rotary Table

In recent years,more and more complex parts need five-axis machine tools for high precision,efficient processing.Five-axis machining center is becoming a major trend in the future development of machine tools.The use of trunnion type direct drive rotary table is one of the mainstream drive methods of five-axis machine tool.In high-precision machining,machine tools thermal deformation error accounts for a high proportion in the total error.Solving the thermal error problem is an important means to improve the machining accuracy of the machine tool.To solve the problem that thermal deformation of direct drive rotary table causes error of five axis machining tools,based on a trunnion rotary table virtual prototype,the thermal characteristics of the table is studied,and the thermal error prediction model is established by temperature rise and offset data.The main contents of this paper are as follows:(1)The functions,components and structure of the virtual prototype are analyzed.The basic theory of thermal analysis and its research methods are given,which can provide reference for subsequent study of thermal characteristics.Considering the actual structure of the table,the main thermal deformation forms are analyzed.Based on the multi-body kinematics theory,an ideal and thermal error motion model is established.The model is applicable to a five-axis vertical machining center with the table studied in this paper.(2)A heat flow model of the table is established to study the generation,flow and dissipation of heat.The heat production mechanism of the heat source is analyzed and its heat production is calculated.Simplify the flow model of the motor coolant,and deduced the theoretical formula of the convective heat transfer coefficient.The contact thermal resistance between the rough surfaces of machined parts is analyzed,and a simplified calculation method is obtained.The results provide accurate initial conditions for the thermal analysis of the table.(3)The simulation work,including the establishment of simulation model,type selection,grid division and solution setting,is analyzed in detail.Based on ANSYS Workbench software,the thermal characteristics of the table are studied.The static results of the temperature distribution and deformation of the table,the temperature of the coolant,the convective heat transfer coefficient,and the dynamic relationship between the temperature rise and the deformation of the selected measuring point are obtained.The influence of the coolant flow and inflow temperature on the thermal characteristics of the table is also studied.Finally,the simulation results are validated from the qualitative and quantitative aspects.(4)Several temperature measurement points are selected and classified by R-type clustering analysis,and the points are further screened by stepwise regression analysis.Based on the multi-linear regression and BP neural network,the prediction model of thermal deformation error is established by using the measured temperature as input and the table surface's offset as output,and the two models are compared.