The feeding zone is equipped with a porous, gas permeable wall section to which a vacuum is applied externally. Intermediate particle air is sucked out of the powdered bulk material through this section. This compacting of the loose material reliably raises the feeding capacity by a factor of two to three whilst maintaining unchanged high product quality.
FET is suitable not only for the feeding zone of the ZSK twin screw extruder, but also for the ZS-B twin screw side feeder that doses powder materials directly into the melt.
Advantages of FET for feed limited compounding processes are: Low investment cost; lower specific energy input; lower production costs through a move to non-compacted and therefore cheaper fillers; improved compound quality through gentler processing of sensitive products due to the higher utilisation of the available processing volume; and reduced dust levels, because back venting is not necessary.
