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Consistent parts protect large disk drives
Closely controlling temperatures in a multi-cavity mold results in uniform shock-absorbing characteristics
By Robert N. Boggs, Southern Technical Editor -- Design News, June 25, 1995
Roanoke, VA-Large disk drives for mainframe computers are precision devices. The precise alignments established during manufacture must survive several potential problems, including possible damage during shipment of the drives, and during their installation at the customer site.
In IBM's 3390 DASD subsystem, the stack of 10.6-inch-diameter disks forms the heart of an 88-lb assembly. Three shock mounts, strategically located with respect to the assembly's center of gravity, protect against vibration. Each mount consists of a butyl rubber cylinder with a welded metal insert and an oval bracket molded in.
This mounting system works well if the three shock mounts are identical. However, IBM encountered problems in obtaining mounts with consistent properties. Investigating the situation, engineers at Acadia Polymers traced the inconsistencies to temperature variations in the multi-cavity mold used to produce the mounts. They discovered that some parts cured faster than others because of the varying temperatures that developed within the molds.
To eliminate these inconsistencies, Acadia decided to elminate the temperature variations. The firm's engineers designed a new 40-cavity mold that operates in a multi-cavity press with a total of 18 separate temperature control zones. Use of that large number of zones helped engineers solve the problem of variable part properties. "Our process evenly distributes and monitors temperature throughout the mold, allowing the rubber to cure uniformly," says Acadia's Chuck Carroll. "Parts are extremely consistent and the rejection rate has been negligible."
Additional details...Contact Chuck Carroll, Acadia Polymers, 1420 Coulter Dr. NW, Roanoke, VA 24012, (703) 265-2700.
