An opportunity is found to reduce set-up time in sheet metal panel bending tasks by deliberately leaving gaps between a segmented punch to allow passage of a bent flange or to adjust the distance between articulated die sections for re-entrant bends. The effects of this practice on part appearance and dimension is addressed to assure part quality. Unconstrained bending in the gap area is modelled, and the gap/thickness ratio is found to be an indicator of part geometry and subjective quality. A zero set-up punch and die set is described for 4-bend parts.

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U.S. Patent #4,489,578
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