Shock effects on the performance of the interface between the moving suspension lift-tab and the ramp in a load/unload drive

The bouncing behavior of the suspension lift-tab at the tab–ramp interface during the unloading process of a hard disk drive subject to external shocks was studied by using a lumped-parameter dynamic model with one degree of freedom in a moving reference frame. A finite element model of the hard disk drive was used to generate the data as input to the lumped-parameter model. This simulation scheme allows easy examination of the effects of individual contributing factors. The effects of the peak acceleration of the external shock pulse, the pivot hub motion, the air bearing suction force and the disk motion on the bouncing characteristics of the lift-tab were studied by evaluating the bouncing distance and bouncing height of the lift-tab as well as the indentation depth at the tab–ramp interface. The simulation results indicate a different behavior of the suspension close to the base plate (B) compared to that close to the cover (C). The bouncing distance and bouncing height were larger for Suspension C compared to Suspension B. For the latter, the motion of the pivot hub is an important contributing factor to the bouncing distance and bouncing height. Moreover, the indentation depth increases significantly with increasing peak acceleration. For suspension C, both the bouncing distance and the bouncing height increase almost linearly with increasing peak acceleration. The vibration of the disk changes the dimple separation height and the air bearing force during an unloading process, thus affecting the bouncing behavior of the lift-tab. The effect of the suction force on the bouncing of the lift-tab is coupled with the disk position. When the lift-tab exceeds the dimple separation height for a disk raised relative to its original position, the suction force can decrease the bouncing height of the lift-tab significantly, compared to the condition without a suction force.