| CNC machine tools are the "working machine" of the manufacturing industry,and the development of the machine tool industry directly affects the development level of a country's manufacturing industry.Among the many error sources that affect the machining accuracy of machine tools,geometric error,thermal error and force error account for 65%of the total machining error of the machine tool,and the more high-precision machine tool and high-precision machining,the thermal error accounts for the proportion of the total error the bigger.As one of the most critical components of the machine tool,the electric spindle plays a decisive role in the accuracy of the machine tool.The water-cooling active control method for the temperature of the electric spindle and the modeling compensation technology for the thermal error of the electric spindle can effectively reduce the thermal error.This paper takes the S5 H CNC machine tool as the research object,and studies the active control technology of the electric spindle thermal error.(1)In order to determine the thermally sensitive parts of the machine tool motorized spindle,a method for analyzing the thermal characteristics of the motorized spindle based on finite element simulation analysis was proposed.By analyzing the structure,thermal error term and heat source of the electric spindle of S5 H CNC machine tool,the thermal load characteristics of the electric spindle are analyzed by using the relevant heat conduction theory of CNC machine tools,and the steady-state temperature field and thermal deformation of the electric spindle model are analyzed by ANSYS Workbench software.The thermal-mechanical coupling finite element model was constructed to theoretically analyze and determine the thermally sensitive parts of the electro-spindle.The thermal error measurement experiment further verified the reliability and effectiveness of the thermalmechanical coupling simulation model.(2)In order to effectively control the temperature change response of the machine tool electric spindle,an active control method of the temperature field of the machine tool electric spindle is proposed.By building a water cooling platform and a temperature control platform,the temperature value of the thermally sensitive part of the electric spindle is used as the control object to compare with the set target temperature,and the electrical signal is transmitted to the I/O box to control the inverter by adjusting the output parameters of the PID module of the PLC.Adjust the flow rate and flow of the water-cooling machine to realize the active control of the temperature of the electric spindle and ensure that the controlled temperature is within the target range,thereby reducing the thermal error.The proposed method can effectively control the temperature change of the electric spindle temperature field.(3)In order to further solve the problem of excessive thermal error of the motorized spindle,a modeling and prediction method of the thermal error of the motorized spindle based on the CSO-RBF neural network was proposed.Based on the temperature of the four measuring points of the main shaft,the water flow rate of the water cooler and the thermal error data of the main shaft,the neural network prediction models of CSO-RBF,PSO-RBF and BP-RBF based on different spindle speeds and different thermal error terms are established to compare Experiments show that the CSO-RBF neural network electric spindle thermal error prediction model has strong robustness and high accuracy.Finally,the compensation application verification is carried out on the 848 D thermal error module of Huazhong CNC system.The experiments before and after the compensation verify the validity of the thermal error prediction model of the electric spindle established in this paper. |
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