Measurement And Modeling Of Thermal Error Of Five Axis CNC Machine Tools With Double Turntable

Five axis linkage CNC machine is the representative of high-end CNC machine tools.The combination of two rotating axes makes the five axis machine tools have many kinds,among which the two turntable five axis CNC machine tool,namely cradle five axis CNC machine tool,is the most widely used.The most important index to evaluate the performance of five axis machine tool is the machining accuracy,which is caused by many factors.Among them,the thermal error caused by the internal and external heat sources of the machine tool accounts for 40-70% of the total error of the machine tool,which is an important error source.Therefore,this paper takes VMC-C50 five axis CNC milling center as the research object,establishes the prediction model of the thermal error of five axis CNC machine tools,establishes the thermal error prediction system,determines the optimal preheating time of five axis machine tools,and improves the machining accuracy of five axis machine tools.According to the structural characteristics of the double-turn five-axis CNC machine tool,the internal and external heat sources and the thermal error characteristics of each moving part are analyzed,and the heat sources of each moving part are quantitatively calculated to obtain the proportion of each heat source of the machine tool,and the overall thermal error of the machine tool.Divided into the thermal error of the spindle-turntable system and the thermal error of the screw-rail system.Aiming at the difficulty of the five-axis NC thermal error measurement,a thermal error measurement scheme and a temperature measurement scheme are designed according to the space-time characteristics of the two.T-type thermocouple and laser displacement sensor are used to build a thermal error measurement platform for CNC machine tools,and measure the thermal error and temperature rise of the spindle-turntable and screw-rail.Aiming at the selection of temperature sensitive points,the temperature measurement points are optimized and selected by the improved K-means algorithm,correlation coefficient method and principal component analysis method.The optimal arrangement position of the temperature sensitive points of the main shaft is obtained by using the dichotomy method,and the thermal error empirical model is optimized.input of.Aiming at the problem of low accuracy of the thermal error model,taking temperature as the input and thermal error as the output,based on the multivariate linear regression model and the autoregressive distribution lag model,the thermal errors of the spindle-turntable and the screw-rail are modeled respectively,and The two models are compared to establish a more accurate thermal error model of a double-turn table five-axis CNC machine tool.Aiming at the complex problem of thermal error control,ANSYS was used to perform thermal-mechanical coupling simulation of the machine tool,and the temperature field and deformation field were analyzed to determine the optimal warm-up time of the machine tool.The thermal error prediction system of fiveaxis CNC machine tools is developed and developed by MATLAB.By inputting corresponding processing parameters,the heat source distribution and thermal error prediction model of five-axis CNC machine tools can be quickly obtained.