Warm Global Customers
With China Plastic Machinery
With China Plastic Machinery
The screw of the plastic extruder is the heart of the plastic extruder and an important component for compressing plastic in the plastic extruder. It is an important component for mixing and pressurizing plastics for extrusion. The screw obtains compression by gradually reducing the screw groove volume with equal distance and unequal depth, equal depth and unequal distance.
Common structure
1. The depth of the gradual change screw groove gradually decreases from the feeding section to the screw head. This type of screw is mainly used for soft and hard polyvinyl chloride, polyolefins, etc. This type of screw is easy to manufacture, but the reasonable design of the feeding section should be equal distance and depth, so the gradual change screw has been gradually eliminated.
2. The metering type has a metering section with equal distance and depth of 4-60 meters in length. The pressure and material flow rate of this screw head are relatively stable, so the extruded products are of good quality and are widely used in polyvinyl chloride, polyolefins and engineering plastics. The feeding section of this type of screw is equidistant and equal in depth, and the depth of the screw groove in the compression section gradually decreases.
3. The compression section of the mutation type is very short, only 1-2D. The feeding section and the metering section are both equidistant and equal in depth, and the metering section is longer. This type of screw is designed for crystalline plastics such as polyphthalamide and polypropylene. Enlarging the mutation zone to about 5D is suitable for processing plastics with a wide melting temperature range.
4. The torpedo head type metering section is equipped with a torpedo head in front. Sometimes a torpedo head can be directly installed in front of the compression section instead of the metering section. Smooth torpedo heads are less used, and most have been changed to torpedo heads with ribs. This type of screw has a large shear force and a good plasticizing effect. It is suitable for the granulation and molding of polystyrene, polyethylene, polyphthalamide, polymethyl methacrylate, and polyvinylidene pyrophosphate. Due to the large friction heat of the torpedo head, a cooling device should be installed.
In summary, the screw structures widely used in extrusion molding are metering type and mutation type.
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