Extrusion forming of internal helical splines

Abstract

An extrusion assembly, which fits into a hydraulic press, includes an upper die plate and a lower die plate mounted to one another by die guide posts. A lead bar is coupled to upper die plate at one end and a hydraulic chuck at its other end and includes helical grooves on its surface that mate with helical protrusions on lead nuts. Hydraulic chuck selectively retains a mandrel assembly. A die shell and insert are mounted concentrically with mandrel assembly and receive a gear blank. A bottom rest assembly is located below die shell and is positioned to receive mandrel assembly. An ejection assembly is positioned between bottom rest assembly and a hydraulic cylinder and includes ejector pins. As hydraulic press pushes lead bar axially through gear blank, lead nuts impart a rotational motion to lead bar, which causes mandrel to move with a helical motion as it is pressed into and through gear blank. Chuck then releases mandrel assembly onto bottom rest assembly and lead bar is retracted. Hydraulic cylinder pushes up on ejection assembly, causing ejector pins to eject the finished gear. Chuck is then lowered to re-attach to mandrel assembly.