Research On Bearing Dynamics Modeling And Preload Optimization Method Of High Speed Motorized Spindle Under Thermal Influence

High-end numerically-controlled machine tools are known as the cornerstone of modern manufacturing,high-performance electric spindles are regarded as the core power components of numerically-controlled machine tools,and angular contact ball bearings are determined to be important supporting components of the electric spindle.A certain pre-tightening force is applied to the bearing during the assembly of the electric spindle,which can guarantee the dynamic performance of the bearing and the adaptability of processing under multiple working conditions.It can be greatly improved the overall performance of the bearing according to the dynamic characteristics of the bearing when considering temperature rise conditions.In this paper,the dynamic model of bearing considering temperature rise is established,and the optimization method of dynamic preloading is given.The main contents of this paper are as follows:(1)Based on Hertz contact theory,outer orbit control theory and quasi statics method.The dynamic model of angular contact ball bearing considering temperature rise,speed and preload is established.The contact characteristics and load variation law between bearing roller and track at high speed are analyzed.The model can be used to calculate various parameters of the bearing,which provides a model basis for bearing preloading optimization.(2)The Newton-Raphson iterative method is used to solve the key parameters of the thermallyaffected bearing dynamic model.The dynamic mapping relationship between the change of main parameters and the change rate after temperature rise and preload under complex working conditions is simulated in MATLAB.It is concluded that the variation of some bearing parameters tends to be stable under the action of preload;The change rate of all bearing parameters convergence under the action of preload.Preload is of great significance to the stable operation of bearings.(3)Based on Hertz contact theory,the finite element model of high speed angular contact ball bearing is established.Based on the ABAQUS platform,the heat distribution of the whole bearing model is obtained.Based on the overall bearing model,a sub model is established to further refine the mesh and accurately calculate the contact load between the bearing roller and the track,and the calculated results are compared with those of the bearing thermal effect dynamic model.The results show that there is little difference between the results of finite element analysis and that of heat effect model,which proves that the heat effect model is correct.(4)The change rate of bearing parameters calculated by thermal effect model is imported into SPSS software,and the principal component analysis method is used to reduce the dimension according to the coupling relationship among the bearing parameters.It is found that the biggest parameter affecting the comprehensive performance of the bearing is the inner rail contact load.Taking this parameter as the optimization object and the rolling element slipping threshold as the optimization standard,the dynamic preloading optimization method of bearing is given.