| 摘要 |
The present invention relates to a sheet plate forming method. While a sheet metal work (10) is being supported by a first die having an accommodation hole having a larger inner diameter than the finishing diameter of a boss (13), extruding is conducted by first punching of a molded portion (20) to form a first convex portion having a first hollow concave portion formed at the inside thereof. Next, while second punching is being applied to the bottom of the first hollow concave portion, the first convex portion is forcedly inserted into an accommodation hole of a second die having the smaller diameter than the first die, and drawing is conducted to reduce the diameter of the first convex portion and extend the height thereof to form a second convex portion and a pocket-shaped retaining support concave portion around the inlet of a second hollow concave portion formed inside the second convex portion. After that, while third punching is being applied to the retaining support concave portion, the second convex portion is forcedly inserted into an accommodation hole of a third die having the smaller diameter than the second die, and final drawing is conducted to reduce the diameter of the second convex portion and extend the height thereof and to cover the second hollow concave portion, thus obtaining the desired boss (13). Accordingly, the boss desirably has the small diameter, high height, and good strength. |
