Dynamic Analysis of High Speed Spindle

Abstract

Assessment of the thermo-mechanical behaviour of machine-tool spindles is a requisite for the reliable operation of high-speed CNC machine tools. The thermal behaviour and applied loads affect the performance of these high-speed spindles. The primary source of heat generation in the spindle is due to friction torque in angular contact ball bearings, cutting forces, centrifugal force, gyratory effects and bearing preload. The spindle shaft is treated as beam element with one translational and one rotational degree-of-freedom at each node. Angular contact ball bearings are modelled to predict heat generation due to load, viscous, and spin-related effects. Mutual interlinkage between the thermal and structural behaviour of both spindle shaft and bearings is modelled using the effects caused due to the thermal expansion and rate of heat generation. The bearing preload is pushed up due to centrifugal force and temperature rise due to high spindle speed. Components matrices are assembled to configure a finite element model for the thermo-mechanical analysis of spindle-bearing systems using Euler-Bernoulli beam theory. Further this work presents ANSYS simulations on CNC spindle system with angular contact ball bearings using 103 Cr1steel material and hybrid type to predict thermal stress. Static and dynamic analysis is carried out on the spindle with and without thermal load and cutting load to predict the displacement and slope.