Views: 0 Author: Site Editor Publish Time: 2026-08-31 Origin: Site
In a twin screw extruder, the side feeder is often used to introduce materials that are difficult to feed through the main feeding system, especially short glass fiber, mineral fillers and other powders. However, installing a side feeder is not simply a matter of choosing an available barrel opening. The position of the side feeder can have a direct influence on melting, dispersion, fiber length retention, residence time and the overall stability of the extrusion process.
For this reason, the side feeder position should normally be considered together with the material, formulation, screw configuration and production requirements.
The material entering through a side feeder does not immediately become part of a finished compound. After entering the twin screw extruder, it still needs to be conveyed, wetted by the polymer melt and dispersed before reaching the die.
This means that the position of the side feeder determines how much processing the material receives after it enters the extruder.
If the feeder is installed too far upstream, the added material may travel through a relatively long section of the screw. This can provide more time for mixing, but it can also expose materials such as short glass fiber to more mechanical stress and shear.
If it is installed too far downstream, the material may have insufficient time to become properly dispersed and homogenized before reaching the die.
Therefore, there is no universal answer such as “the side feeder should always be installed at Zone 5” or “Zone 6 is the best position.” The appropriate position depends on what is being fed and how the entire screw is designed to process it.
For applications such as PA6 GF30, PA66 GF30 and other glass fiber reinforced compounds, short glass fiber is commonly introduced through a side feeder after the polymer has reached a suitable molten state.
This is important because the glass fiber needs to be properly incorporated into the polymer melt. At the same time, excessive mechanical stress should be avoided when maintaining useful fiber length is important for the final mechanical properties.
A side feeder placed too early may expose the glass fiber to a longer mixing and conveying path. A position that is too far downstream, on the other hand, may leave insufficient length for proper dispersion and homogenization.
This is why side feeder position, screw configuration and mixing intensity should be considered as one system rather than three independent parameters.
Side feeding is also widely used for calcium carbonate, talc, mineral fillers and other powders in plastic compounding.
Here, the objective may be somewhat different from glass fiber feeding. The process needs to achieve stable powder feeding and good dispersion throughout the polymer melt, while avoiding excessive accumulation, poor wetting or insufficient mixing.
The position of the side feeder therefore needs to match the behavior of the powder as well as the polymer being processed. A filler with a high loading level can also require a different approach from a formulation containing only a small amount of powder.
This is one reason why simply copying the side feeder position from another extrusion line does not always produce the same result.
The side feeder should not be considered separately from the screw.
For example, the screw section before the side feeder may be designed primarily for conveying and melting the main polymer, while the section after the side feeder may provide the mixing and conveying required to incorporate the added material.
The kneading blocks, conveying elements, mixing elements and their arrangement after the side feeder all affect how much processing the material receives before reaching the die.
L/D is also relevant. A machine with sufficient downstream screw length gives the engineer more room to introduce the material and then provide the required mixing, homogenization and degassing before extrusion.
In other words:
The correct side feeder position is not determined by the barrel position alone. It is determined by what happens before and after the feeding point.
Not really.
A good extrusion design should consider at least:
The polymer and additives being processed
Short glass fiber or powder characteristics
Filler or fiber loading level
Main feeding method
Required dispersion and mixing intensity
Screw configuration
Available L/D
Required production capacity
For liquid additives, the feeding strategy can involve additional considerations and is not discussed here.
This is also why an experienced extrusion manufacturer should not simply recommend the same side feeder position for every customer.
For a glass fiber reinforced compound, the priority may be to introduce the fibers into a stable polymer melt while providing enough downstream mixing without unnecessary fiber damage.
For a high-filled compound or filler masterbatch, the priority may shift toward stable powder feeding, wetting and dispersion.
The machine may look similar from the outside, but the internal screw configuration and side feeding arrangement can be quite different.
At HAISI, we normally determine the side feeder position together with the screw configuration and the customer's actual material and production requirements, rather than treating it as a fixed machine specification.
If you are planning a twin screw extrusion project with short glass fiber, calcium carbonate, talc or other powder fillers, tell us your material, formulation, required output and target product. We can evaluate the feeding position and the downstream screw configuration as part of the complete extrusion process.
