Extrusion is a process used to make products by forcing materials through a die or orifice to form a shape, or to use an extruder to produce semi-finished or finished products.
Single screw extruder screw barrel is the most popular type of extruder. A single screw machine is relatively cheap, simple, and easy to provide continuous output, so it is very popular.
Most extruders are single-screw machines. The screw is the power that pushes the material to and through the mold. The shape is given by the die and post-extrusion molding, and then the product is shaped by cooling while maintaining its shape.