| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for reversely folding a sheet in manufacturing box by which press forming of a ruled line for reverse folding can be reasonably and accurately performed and the reverse folding can be surely performed. SOLUTION: In a punching mold 10 for forming simultaneously a ruled line for folding on a process for punching a flexible sheet material, a ruled line forming body 15 with a ruled line forming part 17 of a projected line with the approximately same width as a ruled line pressing edge 12 at a position facing to the ruled line pressing edge 12 existing at a position corresponding to reverse folding is arranged and a required position of a corrugated board sheet 130 is pinched and pressed by these ruled line pressing edge 12 and ruled line forming body 17 to form ruled lines a and a' on both surface and back face of the corrugated board sheet 130 and reverse folding is performed along the ruled line a.
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