RUNOUT EFFECTS IN THE FAILURE OF THIN-FILM RIGID MAGNETIC RECORDING DISKS

The effect of runout on the variation in friction and wear failures that occur during the sliding of magnetic recording heads against carbon-coated, thin-film disks was investigated. The shape of disk runout was modified by sandwiching metallic shims between the disk and the hub of a test spindle as well as by varying the torque on the clamping screws. These procedures smoothed the complicated runout curve to a simple sinusoid-like curve, and at the same time increased the peak-to-trough runout. Drag tests were conducted on delubricated disks until failure occurred. The test results have shown that smoothing the runout curve to a simple sinusoidal shape increases the time to failure by a factor of ten, provided that the peak-to-trough runout stays roughly below 65-mu-m. Smoothing the runout curve does not prolong the time to failure when the peak-to-trough runout is larger than about 70-mu-m. Elementary dynamical analysis of the head further suggests that small wavelength runouts induce head oscillation and early disk failure.