Ramp-Load Dynamics of Proximity Recording Air Bearing Sliders in Magnetic Hard Disk Drive

Abstract

The revival of dynamic load/unload (L/UL) technology forces us to rethink the air bearing design philosophy, which has traditionally been established for contact start/stop applications. Reliably loading a slider onto a full-rotating disk imposes its own requirements on the slider air bearing designs. This paper addresses the unique design requirements of dynamic L/UL technology, through an investigation of the air bearing characteristics of two proximity recording sliders during a dynamic load process. While the slider/disk contact force is employed as a key indicator of the reliability of the dynamic load mechanism, the air bearing suction force and squeeze flow effect are used to characterize the slider’s dynamics during loading. The effects of the slider’s loading velocity, pitch and roll static attitudes on its dynamic load performance are simulated. In comparison to the positive pressure air bearings, both the enlarged air bearing surface and shallowly recessed cavities of the subambient pressure air bearing sliders generate more squeeze flow, resulting in a rapid development of the air bearing lifting force at a higher attitude. This often leads to a more reliable dynamic load performance. The impact of the air bearing suction force on the slider’s dynamics during loading is determined by the suction force center. A towards-leading-edge suction force not only induces a negative pitch motion during the early stage, but also prolongs the pitch-up process. Both effects can result in a head crash for the slider with a large negative pitch static attitude. In summary, the subambient pressure air bearing sliders that feature the enlarged leading air bearing surface and towards-trailing-edge suction cavities with small recess depth offer a fast pitch-up load performance.