To improve mass production, yield in product and strightness by forming hollow projections through insertion of a plurality of punches into a material, and drawing the hollow projections.
A material 15 is arranged in a space defined by an A dice 13 and a B dice 14 opposite to each other. Then, after a B1 punch 16 and a B2 punch 17 are moved to press the material 15, the movement thereof are restricted and they are positioned by the engagement with the A and B dices 13, 14. The material 15 is pushed rearward to form cylindrical projections 15A, 15B which serve as spaces in a flow inlet area and a drainage area. While the pressing force thereof to the punches 16, 17 are kept, the punch 18 is pressed toward the material 15. Accordingly, a cylindrical projection 15C is formed to serve as an opening to accomodate a function part. The punch 18 is positioned by the engagement with the dices 13, 14 in the similar manner with the punches 16, 17 while it is restricted to move.
NAKAMURA KATSUAKI
NARITA SUSUMU
