Friction Effect on Loading Process and Multiple Stable Flying States of Air Bearing Sliders

One reason to use load/unload (L/UL) technology in hard disk drives is to avoid friction and stiction between sliders and disks during a start and stop process. However, friction between sliders and disks can still exist and has a strong effect on loading because sliders may contact disks during loading. In this paper, a new simplified friction model was proposed and implemented into the L/UL simulation code. Then, we studies two cases: A 10000 rpm server drive and A 1.0 inch Microdrive. It was found that the friction effect is smaller in the server drive case, while it is dramatic in the Microdrive case. Simulation with the proposed friction model shows that sliders will load to the third stable state if PSA is negative and the friction is big enough. In the third stable state, the slider has a negative pitch angle, and its leading edge continuously drags on the disk. In this state, we cannot do any reading/writing, and disks and sliders can be damaged.