What factors need to be considered when designing a screw, and what factors should be considered whe

Designing a high-performance screw that meets these criteria is not an easy task. When designing a screw, the following factors should be taken into account.

1. The characteristics of the material and the geometry, size and temperature conditions when it is added.

The physical properties of different materials, such as extrusion temperature range, viscosity, stability and rheological properties, vary greatly, and therefore the processability is also very different.

The rubber extruder screw is very different from the plastic extruder screw: such as the screw length-diameter ratio, the depth of the screw groove, the screw structure (the plastic extruder screw has a mixing element, a shear element), etc.

The same rubber extruder screw is also different: the cold feed extruder is different from the hot feed extruder screw.

Plastic extruder screws are not the same. For example, polyvinyl chloride and polyolefins are very different. First, the former is an amorphous plastic with high viscosity, sensitive to temperature, and no obvious melting point.

The latter is a crystalline plastic with a low viscosity and a pronounced melting point. Even polyethylene and polypropylene, which are both polyolefins, are not the same.

Even the same polyethylene, but due to different manufacturers, or different batch numbers, its performance is also different. Furthermore, the processing performance of powder and granule is not the same for the same plastic, and preheating and non-preheating also have an impact on the processing performance.

Therefore, different screw designs should be adopted to adapt to different materials.

2. The geometry of the die and the resistance characteristics of the head.

From the working diagram of the extruder, it can be seen that the pattern line of the mouth should be well matched with the characteristic line of the screw in order to obtain a satisfactory extrusion effect. Such as:

1) The high-resistance machine head should generally be matched with a screw with a shallow screw groove depth in the homogenization section, and 2) The low-resistance machine head should be matched with the screw with a deep screw groove in the homogenization section.

3) For the exhaust extruder, the matching of the resistance of the head and the performance of the screw is more important, and if it is not done well, the extruder can not even work.

3. The structure of the barrel and the heating and cooling situation.

According to the theory of solid conveying, the taper and longitudinal groove are processed on the wall of the barrel in the charging section and strongly cooled, which will greatly improve the efficiency of solid conveying. If this structural form of the barrel is adopted, corresponding measures must be taken in the melting section and the homogenization section when designing the screw, so that the melting rate and homogenization capacity are consistent with the conveying capacity of the feeding section.

4. Huahong screw - screw speed.

Since the melting rate of the material largely depends on the shear rate, and the shear rate is related to the number of screw revolutions, the screw speed must be considered when designing the screw.

5. The purpose of the extruder.

When designing a screw, it is important to figure out whether the extruder is to be used as a processed product or as a mixing, granulating or feeding. Because the design of the screw of the extruder for different purposes is very different.

After having a unified view of the criteria for evaluating screws and a comprehensive understanding of the factors that must be considered in the design of screws, the specific design of screws can be carried out.

There are 5 factors to consider when designing a screw:

1) The characteristics of the screw material and the geometry, size and temperature conditions when it is added.

2. The geometry of the die and the resistance characteristics of the head.

3. The structure of the barrel and the heating and cooling situation.

4) Number of screw revolutions.

5. The purpose of the extruder.

1) The characteristics of Mingzhou twin screw materials and their geometry, size and temperature when added 2) The geometry of the die and the resistance characteristics of the machine head 3) The structure of the barrel and the heating and cooling 4) The number of screw revolutions 5) The use of the extruder.