Experimental Study On Characteristics Of Machine Tool Spindle System Under Multiple Working Conditions

Among the errors that affect the machining accuracy of the machine tool,the thermal error caused by the temperature rise of spindle bearing,the rotation error of spindle and the vibration error have the most significant influence on the machining accuracy of machine tool.In this study,a machine tool spindle test-bed with variable speed,variable preload and variable external load has been developed.(1)The whole structure of the machine tool spindle test-bed and the preloading and loading device have been described,the sensors used in the test have been selected,the measurement and control system have been designed,the main structure and the basic principles have been explained.(2)The static stiffness test of the main shaft of the test-bed has been carried out.After three successive loading and unloading processes,the radial stiffness and axial stiffness of the main shaft are obtained,and the reasons for the three curves not coincident are analyzed.The dynamic characteristics of the spindle system are simulated and analyzed in Romax,and the influence rules of preload mode,preload and external load are studied.The modal simulation analysis of the main shaft is carried out in Ansys,and the modal test has been tested.The first six natural frequencies of the spindle are obtained by Ploy Max method and Time MDOF method in LMS Test.Lab,the test results are compared with the simulation results,and the causes of errors are analyzed.The vibration characteristics of the shafting are obtained by considering account the effects of different spindle speed,bearing preload and external load.(3)The measurement method and error separation technology of spindle rotation error are studied.Combined with the structure of the test-bed,the rotation error separation technology combining the reverse method and the bidirectional measurement method are adopted.The test scheme and multiple groups of tests have been designed.The spindle axis trajectory under the influence of different spindle speed,bearing preload and external load have been obtained.(4)Based on the theory of thermodynamics and heat transfer,the friction heat generation of spindle bearing is calculated;the thermal resistance of each node of spindle bearing system is analogized by using the thermal resistance calculation formula of cylinder wall,flat wall and sphere,then the heat transfer equation with bearing as the center is established by using the thermal resistance network method,the temperature calculation formula of bearing outer ring and the temperature rise results of different speeds have been obtained,and the results are compared with test results;the test scheme and several group of tests have been formulated,the temperature rise characteristics of spindle bearing under different spindle speed,bearing preload and external load have been obtained.In this paper,the theoretical,simulation and experimental research on the vibration,rotation accuracy and temperature rise of the machine tool spindle system can provide a certain basis for improving the machining accuracy of the machine tools.