| 摘要 |
The present invention has a blank forming step of forming a sheet-shaped resin blank (3) able to be formed into a box by folding and bending, and a score line forming step of forming score lines (7) in score line forming areas (8) of the blank (3) which are to be bent to form outer edges of the box, to extend in the direction in which the outer edges should extend. In the score line forming step, the score lines (7) are formed in a manner causing grooves (9) to be produced on the back side of each score line forming area (8), along the score lines, through plastic deformation. The blank (3) therefore does not undergo tensile stress pulling on the blank (3) to either side of each groove (9), and thus, does not undergo warping as a whole. The blank (3) thus retains its sheet shape and can be steadily supplied to a packaging machine. |
