| 摘要 |
A work is placed on a pair of dies and a knock out die, and a punch is caused to descend, whereby the work is subjected to bending into a box-shape. In order to reduce a camber generated by an internal stress after the bending, on a surface of the knock out die, widths of friction-reduced regions at side portions thereof are made to be larger than a width of the friction-reduced region at a center portion thereof, with the result that a distribution of friction at the respective portions of the knock out die during processing is improved.
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