Research On Thermal Trror Tnalysis And Tompensation Method Of Electric Spindle In Spiral Bevel Gear Machining Center

With the rapid development of manufacturing industry,the requirements for the machining accuracy of CNC machine tools are higher and higher.As one of the structures of machine tools,the deformation caused by heat in the process of rotation will reduce the machining accuracy of machine tools,so the research on thermal error analysis and compensation method of electric spindle has certain significance for improving the accuracy of CNC machine tools.In this paper,the spindle of large spiral bevel gear machining center is taken as the research object,combined with the thermal error compensation technology of machine tool,a series of research is carried out,the main contents are as follows:(1)Combined with the relevant theory of heat transfer and the structural characteristics of the motorized spindle,the heat source and heat transfer mechanism of the motorized spindle are analyzed.It is known that the main heat source of the motorized spindle is the motor and the bearing.According to the relevant formula,the heat generation rate of the motor,the heat generation rate of the bearing and the heat transfer coefficient between the relevant parts of the spindle are calculated.(2)The transient thermal analysis and thermal structure coupling analysis of the motorized spindle are carried out,and the main heat source and error source of the motorized spindle are found.The effect of different cooling water flow rate on the maximum temperature and thermal deformation in Z direction of the motorized spindle is studied.The results show that the cooling effect is better when the cooling water flow rate is 27 L / min,and the changes of the maximum temperature and the thermal shape in Z direction of the motorized spindle under the conditions of cooling and no cooling are compared.(3)The temperature change and thermal deformation of the uncooled motorized spindle in 400 minutes were measured by temperature rising experiment,and the experimental data were compared with the simulation data.The change trend of temperature and thermal deformation was basically the same,which verified the correctness of the finite element model.(4)According to the fuzzy clustering analysis and grey system analysis,two temperature sensitive points were selected from the original five temperature measuring points.(5)Based on the relationship between the temperature sensitive point and the z-direction deformation of the spindle,the thermal error models of the spindle without cooling and the cooling water flow rate of 27 L / min were established by using the multiple linear regression method and BP neural network method respectively.Compared and analyzed the characteristics of the two thermal error models,the results show that the BP neural network method has better fitting and prediction effect,stronger ability to resist the influence of external factors,simple modeling of multiple linear regression method,less sample demand,and more convenient implementation.(6)The characteristics of three compensation control methods and three compensation strategies are compared and analyzed.The results show that the half closed-loop control method and the origin translation strategy have high cost performance.Finally,based on the analysis of the completed work and the achievements of the research,the ideas and methods of the future research work are put forward.