Improvement of forming limit by rotary nosing with a relieved die

Abstract

Rotary nosing with ‘relieved die’ is proposed for the shrinking tip diameter of a tube. Press nosing or spinning is conventionally used for shrinking the tip diameter. In press nosing, while the forming limit is low, productivity is high. In spinning, although the forming limit is very high, the productivity is very low. The present proposed rotary nosing is an intermediate method that is expected to achieve a higher forming limit than press nosing and realize higher productivity than spinning. In this present research, the forming limit was first examined experimentally and the mechanism was studied by finite element analysis. Based on the results, rotary nosing with a relieved die was proposed. The relieved die consists of three partial cones so that the die geometry is easily cut out using an ordinary lathe. This type of die can be easily and widely applied for industrial use. The effect of the proposed method was numerically evaluated with regard to the pushing force and hoop stress. Finally, the effect of rotary nosing was verified experimentally and the range was clarified where rotary nosing has a higher forming limit than conventional press nosing.