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#153 Design of Compound Punching Dies (2) Punch-Die Relationship in Compound Punching

Category : Die Design
April12, 2013
In compound punching, as shown in Fig. 1, the outer shape is punched from bottom towards the top. Hole punching is done conversely from the top towards the bottom. By doing this, the scrap of hole punching falls down. The (shape blanking) product is inserted inside the die which is in the top die. In compound forming such as compound punching, since it is very troublesome to carry out the operations if the scrap is taken up, very often the design is done so that it falls down. It is necessary to eject out the product that has entered into the die. This can be said to be a problem of compound punching. Fig. 1

Fig. 2 shows the punch-die relationships in compound punching. The parts enclosed in ovals show the respective parts of such relationships. The punch for outer shape blanking is the same size as the product. The punch for outer shape punching is placed below and its die is placed above. The punch for hole punching is placed inside that die. The die for hole punching is prepared inside the die for outer shape punching. A part such as this punch for outer shape punching is called a compound part.
The outer shape is punched from below to above. At this time, a warp is generated so that it gets separated from the punch surface and rises upward, but since the punch for hole punching acts to press from above, in actuality the generation of a warp is suppressed.
Fig. 2

The parts shown here are the primary functional parts of compound punching. To these are added parts such as a stripper, or a part called a knockout which ejects the product that has entered into a die, and all these together constitute a die.

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