Flow-induced vibration of head gimbal assembly

This is a report on ways to reduce flow-induced vibration of a head gimbal assembly (HGA), i.e., windage. The relation between flow-induced force and windage was investigated; as was a statistical approach to optimizing an HGA-arm configuration. The investigated HGAs were set between disks in a spin stand, and their windages were measured by using a laser Doppler vibrometer. The amplitude of sway mode was found to be almost in inverse proportion to the square of its frequency because the power spectrum of the airflow between disks is in inverse proportion to the square of its frequency. Miniaturizing HGAs is therefore an effective way to reduce windage because its natural frequencies then become higher. The windage measured for a HGA with a part length of 12, for example, is 40% less than that of one with a part length of 14.5 mm. Optimizing HGA-arm configurations by the Taguchi Method is also useful for reducing windage. The Taguchi Method is a statistical technique for designing products whose performance is not affected by outside conditions. We used an L8 orthogonal array in this investigation and found that optimizing the actuator arm thickness could reduce windage most effectively, the load-beam bend angle, and the arm shape. The windage of an optimized HGA-arm configuration was reduced to about one third that of the initial configuration. This knowledge will be useful in optimizing the parameters of an HGA and a head stack assembly to obtain hard disk drives with higher track densities.