抄録
In a previous paper, we proposed a two-step cold extrusion method of shaping external spur gears and helical gears. In the present paper, we describe how this filling method is applied to the shaping of internal helical gears. A specially designed mandrel for an internal helical gear utilizing the two-step filling method was used to expand and the inner diameter of the cylindrical workpiece. The specifications of these gears are as follows: module m=1.0, 1.25 and 1.5 mm; helix angle ß=20 deg; number of teeth Z=12-15 and whole depth h=2.00 module. The materials used were aluminum A1200 and low carbon steel S15C. The criterion for shaping complete teeth is discussed primarily in terms of punch pressure and the reduction in the area and the expansion ratio of the inner diameter of the workpiece. The approach that we described here successfully produced a filled up internal helical gear with only a few percent reduction in area. The punch pressure was very low, far below the strength of the punch material.
