Dynamics Of High Speed Spindle And Its Impact On The Stability Of Machining

High speed machining technique is widely used in aviation, automobile and shipping industry, eta. Due to the effects of rotational speed, gyro-effects, and centrifugal force on the stiffness of ball bearing, the stiffness of high speed spindle is dynamic. In this effort, the dynamics of the spindle with respect to the speed and its impact on the stability of machining are investigated.Based on the quasi-static and quasi-dynamic mechanics model of the rolling bearing, a simplified method to solve the dynamic equations of the bearing is proposed by choosing the contact angle as the initial variable. The main parameters of the bearing dynamics including the stiffness are calculated and the results show that the stiffness of the bearing decreases as the speed increase under some axial preload.Considering the dynamic stiffness of ball bearing, a finite element model of spinlde-holder-tool is improved. The effects of spindle speed on the natural frequencies are studied. The influences of the axial preload and the tool overhang length on the natural freuqencies and modal shapes are also investigated. A modal test of the spindle is conducted and the experimental results and the theoretical results are in agreement.Integrating the model of high speed spindle and the model of milling processes, a set of nonsmooth delay differential equations are presented to descript the dynamics of high speed milling processes.. Semi-discretization method is presented for analyzing the stability of periodic orbit of the DDEs. By comparing the stability charts obtained with the effect of the change of the dynamics of the spindle with the stability charts obtained by ignoring effect dynamic stiffness, one could say that the effect of dynamic stiffness of the spindle should not be ignored in the stability analysis of the milling process. In addition, the higher order mode effects on the stability of milling processes are aslo studied in this dissertation.