Ramp load/unload friction dependence on temperature, velocity and ramp material

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.