The Characteristics Of Static And Dynamic Of High Speed Motorized Spindle And Experimental Research

As a tool of machine tools,widely used in various fields of national economy,CNC machine tools with high speed,high precision and high efficiency is a concentrated expression of national technical level and comprehensive strength.High speed motorized spindle is an important power unit for CNC machine to achieve high speed and high efficiency.Its performance directly affects the whole machine characteristics and the quality of the product.In this paper,a three-dimensional finite element simulation model of motorized spindle was established using six degrees of freedom spring unit to replace the bearing based on LMS Virtual.Lab.The electric spindle structure layout,selection of bearing and lubrication cooling method were analyzed.According to the structure of motorized spindle,the static stiffness of the motorized spindle was obtained by finite element static analysis.The effect of bearing pretension and bearing position on the static stiffness was studied.The results show that the static stiffness of the spindle will increase with the increase of the bearing pretension,and the position of the front bearing has a greater influence on the static stiffness of the spindle compared to the rear bearing.Then the method to improve the static stiffness of the spindle was put forward.The dynamic equation of the motorized spindle was constructed,and the modal analysis and harmonic response analysis of the spindle were completed.The influence of the bearing pretension and the bearing position on the natural frequency of the spindle was studied.The inherent frequency of the motorized spindle will be improved along with the increase of the bearing pretension,and the influence of the position of the front bearing compared to the rear bearing on the inherent frequency of the spindle was more obvious.The static stiffness experiment,modal experiment and no-load vibration test of motorized spindle were completed.The radial and the axial static stiffness of the motorized spindle were obtained through radial and axial loading tests.Based on the LMS test system,the free mode and restrained mode experiments of the motorized spindle were carried out by hammering method and the natural frequencies of the spindle were obtained.Comparision of natural frequencies in the free modal and the constrained modal analysis shows that the boundary conditions will affect the system mode,and the frequencies in the constraint mode have the trend toward low frequency.In the spindle no-load vibration experiment,the vibration signal of the spindle front end under different speeds was collected,the frequency characteristics of the maximum vibration acceleration under different speeds were analyzed,and the speed range of steady operation for the electric spindle was obtained.