Patent ID: 7861568

Claim:
A method for press-forming a blank using a press-forming die set comprising: a die having a concave part; a punch disposed in confronting relation to the die and having a convex part for penetrating into the concave part; and a blank holder disposed to surround the punch and having a first bead that restrains an edge of the blank with a constant restraining force during pressing of the blank and a second bead, disposed further to an outside than the first bead such that said first bead is disposed relatively between said second bead and said punch, that restrains the blank edge with a force that varies during pressing of the blank, the method comprising the steps of: forming while restraining the blank with the first bead, which is applying said constant restraining force, and with the second bead, which is applying an intermediate restraining force, said constant restraining force and said intermediate restraining force being sufficient to prevent wrinkling from occurring during forming of the blank; forming while restraining the blank with the first bead, which is applying said constant restraining force, and with the second bead, which is applying a small restraining force, said small restraining force being less than the intermediate restraining force, and whereon said constant restraining force together with said small restraining force do not impede a flow of the blank into the concave part; and forming while restraining the blank with the first bead, which is applying said constant restraining force, and with the second bead, which is applying a large restraining force, said large restraining force being larger than the intermediate restraining force, and wherein said constant restraining force together with said large restraining force are sufficient to inhibit the blank from flowing into the concave part.