A simple tool was developed to evaluate ramp/tab friction during dynamic ramp load/unloads on component level test stands for hard-disk drives. By extracting key attributes of each load/unload time-varying friction cycle, multiple valuable engineering studies were performed. A screening test of candidate ramp materials revealed a strong correlation between friction and wear, with acetal homopolymer and aliphatic polyketone being the most attractive choices. The rate of change of friction with temperature can significantly vary between materials. Data are also presented on friction versus load/unload cycles (showing the onset of wear), load velocity and tab roughness. With knowledge of extreme friction values on each section of the load ramp (slope, top, detent), their influence on actuator torque during load and unload can be calculated and included in tolerance analyses. It is shown that friction can play a significant role in multi-disk drives.
When ramp unloading, the radial distance a slider moves between first touching the ramp and lifting from the disk is called its ''footprint''. Footprints can detract from available recording area. Footprint values were measured for different sub-ambient style air-bearing designs and unloading parameters on a common suspension. Specifically, data was taken over a wide ranging values of PSA/RSA (slider pitch/roll static attitude respectively). Sliders with nominal PSA/RSA regularly lifted gracefully and unaided by suspension limiters within a few mils of travel. As PSA approach zero, however, sub-ambient lifting forces persist, leading-edge limiters engage and footprints extend to 12 mil. Increasing unload velocity increases footprints and slider dynamic vertical motion for nominal PSA/RSA. Surprisingly, for low PSA, slider motion decreases for increasing unload velocity when the leading edge limiter engages.
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