| 摘要 |
The punch is made up of three or more segments which have circumferential grooves on the outside and are mounted on a conical shaft. In operation, as the punch is pressed into the disc of metal, the segments are pushed upwards on the shaft so that their diameter increases by about 0.1 mm compared with that of the punch end. Thus more of the forming pressure is transferred via the teeth to the sides of the 'cup' and deeper drawings can be made without interstage annealing. On withdrawal, the segments retract to the smaller diameter. Minute corrugations formed inside the can are not detrimental. |
