Single screw extruder principle

A single screw is generally divided into three sections in terms of effective length. The effective length of the three sections is determined according to the screw diameter, pitch and screw depth. Generally, each section is divided into one-third.
The last thread of the material port is called the conveying section: the material is not required to be plasticized here, but it must be preheated, pressed and squeezed. In the past, the old extrusion theory believed that the material here was a loose body. Later, it was proved that the movement of the material here It is similar to a solid piston, so as long as it completes the conveying task, it is its function.
The second section is called the compression section. At this time, the volume of the screw groove gradually decreases from large to small, and the temperature reaches the plasticization level of the material. Compression is generated here by the third conveyor section, and is compressed to one here. This is called the compression ratio of the screw - 3﹕1, some machines also have changes, and the plasticized materials enter the third stage.
The third section is the metering section. The material here maintains the plasticizing temperature. It just delivers the melt material accurately and quantitatively like a metering pump to supply the machine head. At this time, the temperature cannot be lower than the plasticizing temperature, which is generally slightly higher.