Study On Thermal-Mechanical Coupled Vibration Characteristics Of Feed System For High Speed CNC Machine Tool

With the rapid development of aerospace,automobile,national defense and other manufacturing industries,the requirements for high speed and high positioning accuracy of CNC machine tool feed system are constantly increasing.However,the heat generated by the high-speed feed system is gradually increased,resulting in an increase in thermal deformation error,a decrease in the structural rigidity of the system,an increase in vibration,and a decrease in the machining accuracy of the machine tool.The existing research focuses on the single thermal performance and mechanical properties of the feed system,and the dynamic performance under the thermo-mechanical coupling is less studied,which makes it difficult to improve the comprehensive performance of the feed system.Therefore,this paper takes the high-speed CNC machine feed system as the research object,and analyzes the thermal characteristics,dynamic characteristics and thermo-mechanical coupled vibration characteristics of the feed system according to the actual working conditions.The specific research is described as follows:(1)We explored the research method of thermo-mechanical coupled vibration for high-speed feed system and formulated the research route of thermo-mechanical coupled vibration,which mainly includes the thermal characteristics,dynamic characteristics and thermo-mechanical coupling vibration characteristics of the feed system.(2)We calculated the heat generation of the heat source,the thermal contact resistance of the key joint surface and the convective heat transfer.Then the moving thermal load is applied in the simulation model to complete the steady-state temperature field,transient temperature field and thermal-structural coupling analysis.The research shows that the maximum temperature rise of the feed system is 21.08OC and the maximum thermal deformation is 17.264um.In view of the severe heat generation in the local area,we designed a local cooling device and analyzed the impact factors affecting the cooling effect.The results show that the parameters such as flow rate and air temperature have a great influence on the cooling effect,and the cooling device are optimized accordingly.(3)We calculate the cutting excitation force,establishing a joint analysis model such as bearing pair,nut pair and guide rail pair,calculating the equivalent kinetic parameters of the joint surface,then completed the modal analysis and harmonious response analysis.The results show that the first natural frequency is 330.68Hz and the maximum amplitude is 18.6um in the frequency range of 300?500Hz.(4)Considering the influence of thermal load on the stiffness of the joint surface for bearing pair,screw nut pair and slider guide pair,a thermo-mechanical coupling model is established to obtain the steady-state and trsmsient thermo-mechanical coupling vibration characteristics.The influence law of the thermo-mechanical coupling effect on the dynamic response performance is analyzed.The results show that the thermal-mechanical coupling effect causes the natural frequency to decrease and the vibration amplitude to increase by 21.0%,especially in the low frequency stage.Therefore,the local cooling treatment of the feed system and the improvement of the joint surface stiffiiess are proposed to improve the dynamic performance.(5)The experimental verification of thermal and thermo-mechanical coupling vibration characteristics for feed system is completed.Compare experimental results with simulation results,the maximum temperature error is 3.4%,which verifies the correctness of the theoretical method and the analytical model;The maximum temperature obtained by the test is 39.7?,indicating that the thermal effect generated by the high-speed feed system is large;The error of vibration amplitude between experiment and theory is 12.5%,indicating the correctness of the thermo-mechanical coupled vibration research method;The experimental results show that the vibration amplitude increases by 19.7%under the thermal-mechanical coupling effect,which indicates that the thermal-mechanical coupling effect should be considered in Ihe study of dynamic characteristics for high-speed feed system.The theoretical methods,simulation and experiment of thermal characteristics,dynamic characteristics and thermo-mechanical coupled vibration characteristics are studied in this paper,which provide theoretical basis for the design of high-speed feed system.The designed local cooling device can effectively reduce the thermal deformation of the feed system and improve the processing accuracy.