Experimental and numerical analysis of friction in high aspect ratio combined forward-backward extrusion with retreat and advance pulse ram motion on a servo press

• A forming method with pulse punch ram motion was applied to combined forward-backward extrusion with a high aspect ratio.
• The friction at the specimen–punch interface in the forming method was estimated from the material flow of the specimen.
• The punch wear in the proposed forming method was 1.1–1.6 times larger than that in the conventional forming method.

A method for maintaining lubrication in the backward extrusion of deep holes for lightweight structural components is proposed utilizing a servo press and a punch with an internal channel for liquid lubricant supply. In this forming method, the punch is pushed into the specimen with a servo press in a manner that combines pulsed and stepwise modes. Sufficient liquid lubricant is periodically supplied to the deformation zone through the internal channel upon the retreat of the punch. This forming method with pulse punch ram motion was tested in combined forward-backward extrusion process with a high aspect ratio (height/diameter) in this study. The material flow of the aluminum specimen during the extrusion with pulse punch ram motion was investigated to determine the coefficient of shear friction at the specimen–punch interface. The punch wear was assessed by a finite element analysis of the material flow of the specimen during the extrusion with pulse punch ram motion.