| 摘要 |
PROBLEM TO BE SOLVED: To provide a method to lighten the member by forming a peripheral wall protruded towards both sides of the non-processed part; wherein a disc-like plate steel material is pressed at its peripheral part into a radius direction during rotating, and is protruded towards both sides of the non-processed part during being thickened. SOLUTION: The non-processed part 14 of a material 10 is nipped, held, and rotated between a pair of moldings 100 and 200, and then pressed by a molding roller 300 being opposed to a peripheral part 15 of the material. The molding roller 300 has a valley-shaped molding face 310 expanding to the outside, at the peripheral face. By pressing the molding face 310 to the peripheral part 15 of the material 10, the peripheral part 15 of the material is compressed in a radius direction, and thickened in a shaft line direction so as to protrude a peak part 16 with the same shape as the valley-shaped molding face 310 towards the both sides of the non-processed part 14. Thereafter, the molding roller 300 is sequentially changed to a roller comprising a semi-circular molding face, a semi-oval molding face, and a flat and shallow groove molding face. Further, at the final stage, a molding roller having a shallow groove molding face on its flat bottom face is used so as to obtain the peripheral wall with a desired shape. |
