Common Structure Of Plastic Extruder Screw

The plastic extruder screw is the heart of the plastic extruder, and it is an important part of compressing plastic in the plastic extruder. It is an important part of extruding the plastic by mixing and pressurizing it. The screw obtains the compression effect by gradually reducing the volume of the screw groove through equal distances and different depths, equal depths and different distances, and different depths and different distances.
1. Gradual type The depth of the screw groove gradually decreases from the feed section to the screw head. This type of screw is mainly used for soft and hard PVC.
olefins, polyolefins, etc. This type of screw is easy to manufacture, but the reasonable design of the feeding section should be equidistant and equal depth, so the gradual change screw has been gradually eliminated.
2. Metering type It has a metering section with a length of 4-60 and equal distance and depth. The pressure and material flow at the head of the screw are relatively stable, so the extruded products are of good quality, and are widely used in polyvinyl chloride, polyolefin 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. Mutation type The compression section is very short, only 1-2D. Both the feeding section and the metering section are equidistant and equal in depth, and the metering section is longer. This screw is designed for crystalline plastics such as polyamide and polypropylene. Enlarging the mutation zone to about 5D is suitable for processing plastics with a wide melting temperature range.
4. Torpedo head type The torpedo head is installed in front of the metering section. Sometimes it is also possible to install the torpedo head directly in front of the compression section instead of the metering section. Smooth torpedo heads are rarely used, and most of them have been changed to ribbed torpedo heads. This kind of screw has high shear force and good plasticizing effect. It is suitable for polystyrene, polyethylene, polyamide, and polymethacrylate. , The granulation and molding of polyvinylidene diazepam. Due to the high frictional heat of the torpedo head part, a cooling device should be installed.