Browse Prior Art Database

Clamping of Magnetic Disk Stack with a Top Ring

IP.com Disclosure Number: IPCOM000049957D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Prater, WL: AUTHOR

Abstract

This article describes a method to reduce disk distortion in a Head Disk Assembly (HDA). The magnetic disks must be held rigidly to prevent radial migration due to thermal shock, start/stop acceleration impulses, and centrifugal force which would cause data track and servo track runout, thereby degrading the file's read/write performance. The disk stack is held in place by a bell-shaped clamp which contacts the upper most disk directly, causing severe distortions predominantly in the top disk. The distortions have been isolated to the disk inside diameter, near the bell clamp interface, and occurred when the six bolts clamping the disk pack together were torqued to generate 10,000 pounds of compressive force.

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Clamping of Magnetic Disk Stack with a Top Ring

This article describes a method to reduce disk distortion in a Head Disk Assembly (HDA). The magnetic disks must be held rigidly to prevent radial migration due to thermal shock, start/stop acceleration impulses, and centrifugal force which would cause data track and servo track runout, thereby degrading the file's read/write performance. The disk stack is held in place by a bell-shaped clamp which contacts the upper most disk directly, causing severe distortions predominantly in the top disk. The distortions have been isolated to the disk inside diameter, near the bell clamp interface, and occurred when the six bolts clamping the disk pack together were torqued to generate 10,000 pounds of compressive force.

The complex mechanism of the clamping distortion is described below. Six bolts are torqued to deflect the bell clamp toward the hub to produce 10,000 pounds of force (see Fig. 1). The 60,000 psi of stress at the bell clamp disk interface exceeds the elastic limit of the disk, forcing it to plastically deform at the bell clamp disk interface. The six bolts produce stresses varying as much as 67 percent on the bell clamp near the bolts. This non-uniform stress is transmitted to the bell clamp lip, where it contacts the top disk. Stress on the top disk at the inside diameter varied sinusoidally with six minima and maxima seen around the circumference every 60 degrees.

Deep drawing operations during the manufacturi...