Extrusion describes the process by which a polymer melt is pushed across a metal die, which continuously shapes the melt into the desired form. A variety of polymer products, including seals, tires, wires and cables, and tubes and pipes, can be extruded with suitable extruders and shaping methods at different operating conditions.

Extrusion processes are sometimes facilitated by a metal insert which moves together with the melt. Wire coating is a straightforward illustration of an extrusion process assisted by the motion of a solid body; extrudate profiles reinforced with a metal insert are another family of such applications. In these cases, next to the prediction of the extrudate shape, it can be also interesting to predict the heat transfer that occurs between the melt and the solid body in motion (see Heat Transfer).

A wide range of extruders is available. The uniformity of the end product (the extrudate) will depend upon the thermal and physical properties of the polymer, its behavior under given operating conditions (for example, inlet flow rate), and the die design.

For a given die design, you can use Ansys Polyflow to analyze the extrusion at different operating conditions, in order to determine the optimal conditions at which the extrusion through that die should be performed. This is referred to as direct extrusion. Conversely, you can specify the desired shape of the extrudate, and have Ansys Polyflow determine the shape of the die. This second case is referred to as inverse extrusion.