The injection molding machine screw has the following characteristics:
1. The length to diameter ratio and compression ratio of the injection screw are relatively small;
2. The screw groove of the homogenization section of the injection screw is relatively deep;
3. The feeding section of the injection screw is longer, while the homogenization section is shorter;
4. The head structure of the injection screw has a special form.
5. When the injection screw is working, the plasticizing capacity and melt temperature will change with the axial displacement of the screw.
According to its adaptability to plastics, injection molding machine screws can be divided into general-purpose screws and special screws. General-purpose screws are also called conventional screws, which can process most of the thermoplastic plastics with low and medium viscosity, crystalline and non-crystalline civilian plastics. Engineering plastics are the most basic form of screws. Corresponding to them, there are special screws, which are used to process plastics that are difficult to process with ordinary screws. According to the screw structure and geometric characteristics, it can be divided into conventional screws and new types of screws. Also known as three-section screw, it is the basic form of screw. There are many new types of screw, such as separate screw, split screw, corrugated screw, screw without metering section, etc.
The effective thread length of conventional screw is usually divided into feeding section (conveying section), compression section (plasticization section), metering section (homogenization section). According to different plastic properties, it can be divided into gradual, abrupt and general screw.
Gradual screw: The compression section is longer, the energy conversion is gentle during plasticization, and it is mostly used for PVC and other plastics with poor thermal stability.
Abrupt screw: The compression section is shorter, and the energy conversion is more intense during plasticization. It is mostly used for polyolefin, PA and other crystalline plastics.
General-purpose screw: A general-purpose screw with relatively strong adaptability, which can adapt to the processing of a variety of plastics, avoid frequent screw replacement, and help improve production efficiency.
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