The Use of the Six Sigma Approach to Minimize the Defective Rate from Bending Defects in Hard Disk Drive Media Disks

Abstract

The objective of this research is to reduce the defective rate from bending defects in media disks of hard disk drives by finding an optimal machine setting in the assembly process. The Six Sigma method was applied to find out the factors which statistically affected the bending value and to obtain the optimal setting of those factors. It was found that a minimal bending value was achieved with the setting of the clamp screw torque at 3.25 in-lb, the screw bit height at 3.00 mm., and the vertical force on the disk clamp and the motor at 2.50 lbs. With this optimal setting, the process capability index Cpk increased from 0.69 to 1.39, the mean bending value decreased from 5.12% to 3.43%, and the defective rate reduced from 32,219 ppm to 39 ppm.