Mechanical principle of single screw extruder

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 diameter of the screw, the pitch and the depth of the screw, which are generally divided into one third each.

The last thread of the material mouth begins to call the conveying section: The material here is required not to be plasticized, but to be preheated and compressed. In the past, the old extrusion theory believed that the material here is a loose body, and later it was proved that the movement of the material here is similar to a solid piston, so as long as the conveying task is completed, it is its function.

The second section is called the compression section. At this time, the volume of the screw groove gradually becomes smaller, and the temperature must reach the plasticization level of the material. The compression generated here is from the third section of the conveying section, and it is compressed to one here. This is called the compression ratio of the screw - 3:1. Some machines also change, and the plasticized material enters the third section.

The third section is the metering section, where the material maintains the plasticizing temperature, just like a metering pump to accurately and quantitatively transport the melt material to supply the machine head. At this time, the temperature cannot be lower than the plasticizing temperature, generally slightly higher.

Nanjing Haisi Extrusion supply single screw extruder, especially for plastic recycling. 

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