Single Screw Extruder

Single screw extruder is one of the core operations in polymer processing and is also a key component in many other processing operations. The foremost goal of a single screw extrusion process is to build pressure in a polymer melt so that it can be extruded through a die or injected into a mold. Most machines are plasticating: they bring in solids in pellet or powder form and melt them as well as building pressure.

Single screw extruder can process all kind of plastics products with auxiliary machines concerned, such as film, pipe, stick, plate, thread ,ribbon, insulating layer of cable, hollow products and so on .It is also used in graining. The machine design is advanced, production capacity is high, plasticization is good, and energy consumption is low. The extruder adopts hard gear surface for transmission. It has advantages of low noise, smooth operation, large loading, long use-life and so on

Structure of single screw extruder

1. Feed section

2. Compression section

3. Metering section

The feed section is the part of the screw where the unmolten polymer enters into the barrel. The rotating screw moves the material along the heated barrel where it starts to melt.

In the compression zone, gases like air and volatiles like moisture, are being removed. In the compression zone, the flight depth decreases and gases are pushed back into the direction of the hopper.

Finally, the material enters the metering section. In this section, pressure is generatedwhich enables the material to be conveyed into the shaping area, like feed block or film die.

The compression ratio of the screw is the ratio between the flight depth of the feed section and the ratio of the metering section.

Most screws have a flight helix that is equal to the diameter of the screw.

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