Continuous Extrusion by Viscous Drag

A multistage continuous extrusion process based on a new concept is described and studied. The billet is driven through a series of dies by the viscous drag of a fluid flowing along its perimeter, allowing for an unlimited length of the extruded product. Design parameters are obtained from an analysis of the flow and of the stresses in the billet. The geometry of the dies, the extrusion chambers, and the optimal flow characteristics are determined. Technical problems such as buckling of the billet and temperature rise of the fluid are discussed. Experimental results with a one-stage unit are given and compared to the theoretical prediction.