 There are two major types of dies used in overjacketing extrusion, both based on an overall crosshead design.Regardless of die type used, the polymer melt is often extruded at a rate less than the speed of the bare wire that is drawn through the die, typically on the order of 1-4 times the speed of the melt.This causes the polymer jacket to extend, thin, and tighten around the central wire, increasing adhesion of the new layer.