Rich design concept of double alloy screw

Update: 2021/06/25
Summary:

The bi-alloy screw with excellent performance must have […]

The bi-alloy screw with excellent performance must have a rich set of design concepts behind it. When designing the twin alloy screw, the following factors should be considered comprehensively:
 A: The characteristics of the material and its geometric shape, size and temperature when it is added.
The physical properties of different materials are very different, so the processing performance is also different, and there are different requirements for the structure and geometric parameters of the single-screw extruder.
The screw of the rubber extruder is very different from the screw of the plastic extruder: such as screw length to diameter ratio, screw groove depth, screw structure (plastic extruder screw with mixing elements,
Shearing element) etc.
The same rubber extruder screw is also different: the cold feed extruder screw is different from the hot feed extruder screw
Plastic extruder screws are also different. For example, there is a big difference between polyvinyl chloride and polyolefin. The former is an amorphous plastic with high viscosity, which is relatively sensitive to temperature and has no obvious melting point. The latter is a crystalline plastic with low viscosity and a clear melting point. Even polyethylene and polypropylene, both of which are polyolefins, are different. Even the same polyethylene, but due to different manufacturers, or different batch numbers, their performance is also different. Furthermore, for the same plastic, the processing properties of powder and granules are different, and preheating and non-preheating also have an impact on the processing performance. Therefore, different screw designs must be adopted to adapt to different materials.

B: Die geometry and head resistance characteristics and other extruder related information: Die mold characteristics must be well matched with the characteristics of the single-screw extruder in order to obtain satisfactory extrusion results. If the head pressure is high, a single screw extruder rod with a shallow groove depth in the homogenization section is generally required; while the resistance of the head is low, it needs to be matched with a single screw extruder with a deep groove in the homogenization section; design It should be considered beforehand whether it is used for processing products or for other purposes such as mixing, granulating or feeding. Obviously. Single screw extruders for different purposes should be very different in design.

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