Precision forging of helical gear with axially driven die

摘要

In cold forging, a high forming pressure is required to fill the billet material into the corners of die cavity due to the high flow stress of the steel. To reduce the forming pressure, a method employing an axially driven die has been proposed by the authors. In the present paper, the proposed method is applied to precision forging of helical gears: a movable die is helically driven while the billet is squeezed by the punch. It is considered that the frictional force at the billet-die interface helps to push the billet material into the corners of the tooth cavity by the movement of the die. Thus, the billet material flows easily into the corners of the tooth cavity and the forming pressure is reduced. The forming pressure and the filling characteristics of the tooth cavity are examined by experiments using lead as a model material. The results show that the forming pressure of the helical gear is reduced greatly when the die is helically osciallated.