| 摘要 |
PURPOSE:To prevent occurrence of ruptures on the corner of outer face by putting an Al material made by cutting of corner angles of a flat square Al material in a square hole and press forming by a punch. CONSTITUTION:Corner angles of a flat square Al material 4a are cut off 13 and put in a hole 3. Then, triangular columnar spaces are formed at four corners of the bottom of the hole. The length of cut off part 13 differs according to the size, thickness etc. of the Al material 4a. However, it is desirable to make the length of cut off part 1/1-1/3 of the length of the side 14. Next, when press forming is made by a punch 1, oil applied on the outer surface of the Al material escapes from the periphery of the hole 3 to the opening of a die 2. Thus, occurrence of rupture due to blocking of the oil to four corners of the bottom of the hole 3 as appeared in the past can be prevented. |
