What factors should be considered when designing a scre […]
What factors should be considered when designing a screw It is not an easy task to design a screw with excellent performance that meets the above standards. When designing the screw, the following factors should be considered comprehensively
The characteristics of the material and its geometric shape injection screw barrel , size and temperature when it is added.
The physical properties of different materials (such as extrusion temperature range, viscosity, stability and rheological properties) are very different, so the processing properties are also very different.
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 element, shear 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, polyvinyl chloride and polyolefin are very different. The former is an amorphous plastic, which has a high viscosity, is more 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 properties are also different. Furthermore, for the same plastic, the processing properties of powder and granules are different, and preheating and non-preheating also affect the processing performance.
Therefore, different screw designs must be adopted to adapt to different materials.
The geometry of the die and the resistance characteristics of the machine head.
It can be seen from the working drawing of the extruder that the character line of the mouth model must be well matched with the characteristic line of the screw to obtain a satisfactory extrusion effect.