| 摘要 |
PROBLEM TO BE SOLVED: To prevent damage by abutting in forming a rectangular flange next orthogonally crossed with the rectangular flange in the case that the rectangular flange which is previously bent is present at the time of bending a box by forming plural slits in edge parts for pressure-welding a sheet-shaped work of a bending die for bending by ironing a box-shaped product or the like. SOLUTION: The plural slits (relieves) 9 are cut in prescribed positions in a longitudinal direction in tip parts for pressing the work of a lower die 5. Each cut position in the longitudinal direction is decided by dimensions of a long side and short side of the prescribed box-shaped product. When an angle for correcting a spring back is (90+α) deg. at the time of secondary bending of a flange, the width by which thickness of the pressure welding part at the tip of the lower die 5 is abutted on the edges on the side of the flange parts 1 by the primary bending is relieved, that is, when the thickness of the work W is expressed by (t), it is defined as the dimension of about 3t. The number of slits 9 may be provided by the number compatible to the prescribed plural box-shaped products on the same lower die 5.
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