plastic extruder screw structure

Different Materials need different screw structure. Usually here are five zones in a thermoplastic extruder screw. Well,the terminology is not standardized in this industry. So there are different names of these five zones.

The detailed explanation of the five zones are as follow:

1.Feed zone of plastic extruder screw. Also called solids conveying. This zone feeds the thermoplastic materials  into the screw, and the channel depth is usually the same throughout the zone.

2. Melting zone of plastic extruder screw. Also called the transition or compression zone. Most of the mateiral is melted in this zone, and the depth of the channel gets progressively smaller.

3. Metering zone of plastic extruder screw. It is also called melt mixing. Where the channel depth is again the same throughout this zone, it melts the last particles of the polymer resin.and mixes it to a uniform temperature and compount.

4. Decompression zone of plastic extruder screw. It is  about two-thirds down the screw, the channel suddenly gets deeper, which relieves the pressure and allows any trapped gases (moisture or air) to be drawn out by vacuum pump.

5. Second metering zone of plastic extruder screw. It is like the first metering zone, but it gets greater channel depth, and repressurizes the melt to make it through the resistance of the filter screens and the die mould.

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plastic extruder screw