Experimental study on whirling, flying and tilting motions of a 3.5Â in. FDB spindle system

This research develops an experimental method to measure the motion of a FDB spindle system with a 3.5 in. disk by using three capacitance probes fixed on the xyz-micrometers, and it shows that a FDB spindle system has whirling, flying and tilting motions. It also shows that the whirling, flying and tilting motion converge very quickly to the steady state at the same time when the rotor reaches the steady-state speed. However, they are quite large even at the steady state when they are compared with the 10 nm flying height of a magnetic head. For the FDB spindle system used in this experiment, the whirl radius and the peak-to-peak variations of flying height and tilting angle at the steady-state speed of 7200 rpm are 0.675 μm, 30 nm and 5.785°×10−3, respectively, so that the radial motion of the FDB spindle system exceeds a track pitch of a 3.5 in. HDD with 90,000 TPI.