Drawing:
Progressive drawing operations can be accomplished in a progressive
die to fabricate both simple and complex shells. This may be
done entirely within the progressive die or through the use
of more elaborate transfer station mechanisms.
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Typically, there are three types of
draw-die cutoff techniques:
Blank Through:
Initial die construction is quite simple and, therefore, less
expensive. In most cases, the progressive die will run at higher
rates. The cutoff station will not require any special maintenance.
Simple die maintenance and a higher stamping rate result in lower
piece part costs.
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Pinch Trim:
Die construction is somewhat more complex than the simple Blank
Through process. Depending on part geometry, run rates are only
slightly slow-er than the Blank Through approach. Pinch Trimming
produces a feathered edge along the rim of the drawn part. Because
of the greater complexity of the tool, die maintenance is more
involved than that associated with a Blank Through tool.
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Shimmy Trim:
The Shimmy Trim process produces a square edge on the open end
of the drawn shell. This is an edge configuration that is frequently
required in applications calling for welding or brazing of other
components to the trimmed end of the drawn shell. Due to the moving
die components in the Shimmy Trim cutoff station, the stamping
rate is quite low relative to the Blank Through and Pinch Trim
techniques. Die maintenance is extremely demanding and both the
tool cost and piece part price are quite high.
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