外径絞りを伴う冷間押出しによる平歯車の成形

概要

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The shaping of spur gear by cold extrusion through reducing the outer diameter of workpiece is examined experimentally. The specifications of gear tested are as follows : module m=1.0,l.25,1.5,pressure angle α=20°, number of teeth Z=22,18,16,whole depth h=2.25m, bore diameter di=0∿15mm. The material used is low-carbon steel, JIS S15C. It if found that this method can produce much better shaped spur gears, having complete tooth, than the extrusion without reducing the outer diameter of workpiece. Especially, even the gear having relatively small size bore can be also well shaped. And the higher the reduction in area, that is, the larger outer diameter and/or larger inner diameter, the higher punch pressure is needed and the better shaping can be achieved. The minimum punch pressure to shape complete tooth is related to the reduction in area, and width of defective tooth, appeared on near the both end parts, seems to be controlled by the punch pressure.