Plastic extrusion is one of the most widely used manufacturing processes for plastic moulding as well as one of the most widespread manufacturing processes for thermoplastics. It is a method of forming a continuous profile with a constant cross-section by forcing a thermally melted polymer material through a head die under pressure by means of the extrusion of a screw or plunger. The extrusion process mainly consists of the addition of material, melt plasticization, extrusion, shaping and cooling.

The extrusion process can be divided into two stages: the first stage involves plasticizing the solid plastic (i.e., turning it into a viscous fluid) and passing it under pressure through a specially shaped bush to form a continuous body with a cross-section similar to that of the bush; the second stage involves using suitable methods to make the extruded continuous body lose its plastic state and turn it into a solid, i.e., the desired product.

In recent years, with the emergence and development of modern plastic extruder technology, the theory and technology of extrusion molding has been deepened and expanded, the means of research and development of new products and new processes have been strengthened, and various structures and functions of extrusion equipment have been produced, such as multi screw extruders, reactive extruders and combined extruders, etc.; the types of materials, product structures and product forms that can be extruded and processed are also increasing; at the same time, with the increasingly widespread application of computer technology in the extrusion IU molding process, there are also new extrusion molding technologies such as reactive extrusion, auxiliary extrusion, extrusion foam, co-extrusion, high-speed extrusion, precision extrusion and near-melting point extrusion.