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Automatic Adjustment of In-Line Gram Form Process

IP.com Disclosure Number: IPCOM000099561D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Roach, DL: AUTHOR [+2]

Abstract

The preload and formed area flatness of the suspension for a read/write head in a hard disk drive varies considerably as a result of small variations in the metal thickness. Historically, a single form mandrel is used to form these suspensions. By selecting one of several form mandrels based on a measurement of the actual metal thickness, rather than a single form mandrel, much more consistent parts are produced.

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Automatic Adjustment of In-Line Gram Form Process

       The preload and formed area flatness of the suspension
for a read/write head in a hard disk drive varies considerably as a
result of small variations in the metal thickness. Historically, a
single form mandrel is used to form these suspensions.  By selecting
one of several form mandrels based on a measurement of the actual
metal thickness, rather than a single form mandrel, much more
consistent parts are produced.

      The purpose of the suspension assembly in a disk drive is to
hold the read/write head against the disk with a preload force to
maintain the proper gap necessary for good magnetic performance.
This preload is also commonly called "gram load".  The preload is put
into the suspension by a forming process called the gram form
process, which puts a curved area into the suspension, thus creating
a spring. This preload must be held within certain limits to achieve
proper performance.  A formed area flatness measurement is made to
determine the amount of curvature.  Curvature is controlled closely
such that vibrations within the suspension are minimized.

      The preload and formed area flatness, which are set in the part
during the form process, are highly dependent on the thickness of the
metal that the suspension is made from. Normal variation in metal
thickness, both from reel to reel and within a reel, causes the
preload of parts formed by a single form tool to vary more than is
functionally allowed. Thus, using a single form tool, some parts are
adjusted or scrapped.  On those parts that are adjusted, the formed
area flatness must be kept within the functional specification.
Parts with flatness that is beyond the allowed limits are scrapped,
as there is not a way of reworking fl...