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Fig.7.23 is the mold with undercut-forming pins(hole forming mandrel)8 actuated by cam within grooves 4. The pins which form the holes of the elbow pipes shown in the drawing are actuated by cams fixed to the stationary part of the mold. The angle of the cam groove should be 30-40. For long paths the pulling force necessary is considerably increased.
Operation: upon opening of the mold, rollers 15 slide in cams 4 fixed to the stationary supporting plate 2, the shaft of which is screwed into plate 16. These rollers 15 pull out the hole-forming pins 8 from the workpieces. Upon contact of ejector 13 with the stop of the machine, the ejector pins 23 lift the workpieces out of their nests.
Advantage: the mold is fully automatic, and is highly productive and safe.
Disadvantage: on account of cams with groove, the mold is fairly large.
The shape of the elbow pipes is spark erosion machined into blocks 26 and 24. The lower and upper parts of mold require careful fitting, otherwise workpieces will not be aesthetically accep table. Instead of spark machining, those shapes can be cold hobbed, but in this case it is advisable to prepare each nest separately and to assemble them in the mold
