Dynamic characteristics of drilling spindle supported by radial permanent magnet bearings

Abstract

This paper presents the drilling spindle dynamic and harmonic characteristics supported by radial permanent magnet bearings (PMBs). Initially, multi-ring radial PMB is designed in proportionate to the dimensions of drilling spindle using Coulombain model and vector approach. Dynamic analysis of spindle is carried out for three different combinations between conventional angular contact bearings (ACBs) and PMBs. First, the spindle was supported by only ACBs. Second, ACBs were completely replaced by radial PMBs and one ACB was used in between two PMBs making it as a hybrid bearing set (HBS) in the last case. The effect of bearing preload, bearing span and cutting force on the spindle natural frequency, harmonic frequency and critical speed of drilling spindle system was investigated through rotor dynamic analysis. This analysis focuses on the feasibility of successful usage of HBS in drilling machine spindles with higher critical speeds and maximum amplitudes produced due to chattered vibrations and tangential cutting forces. © 2019 Elsevier Ltd.