Vibration analysis of disk-spindle due to ball bearing excitation

Large capacity magnetic disks require a head postioning accuracy in the order of a few micro-meters. This implies a technology to master the difficult problems of the disk-spindle assembly vibration. The following subjects are studied in this paper : (1) The gyroscopic effect on the natural frequency of the rotor-bearing system is experimentally made clear by exciting a rotating spindle. (2) The whirling force acting on the spindle system is dominantly caused by slight deformations on the ball bearing races. (3) It is shown numerically as well as experimentally, considering whirling direction, that the resonance causing a head positioning error results from a coincidence of rotor natural frequency and the ball bearing excitation frequency.