Effects of compliance of hydrodynamic thrust bearings in hard disk drives on disk vibration

For cantilever-shaft design 2-disk hydrodynamic bearing spindle motors, the compliance of the thrust bearing has little effect on the radial operating vibration amplitudes which are the major contributor to the track misregistration in hard disk drives. At the low frequency range (<300 Hz), the compliance of the thrust bearing has great effect on the axial vibration amplitudes. However, the disk flexibility and/or disk clamping condition have more effects than the compliance of the thrust bearing on the axial operating vibration amplitudes at the frequency range of 300-800 Hz. Magnetic preload may contribute equivalent vibration amplitudes but consumes much less power than the hydrodynamic preload does.