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If your extruder is not degassing properly, the signs show up in the product. Bubbles, porosity, odour, poor surface finish. The vacuum pump is running, but it is not getting the job done.
There are usually two reasons. Either the vacuum has been turned down to stop melt coming up the vent, or the vent has partly blocked with material and is not drawing properly. Sometimes both.
Improving degassing means keeping the vent open and being able to apply full vacuum without flooding. That is what a vent port stuffer is for.
Screwtech Engineering stuffers use a self-wiping twin-screw design. The screws convey any rising melt back down into the barrel and wipe each other clean as they turn, so the vent does not block. Precision tolerances allow full vacuum to be drawn, removing moisture and volatiles properly.
With the vent under control, you can also make better use of available barrel length and vent port positions, and the screw configuration becomes less critical. Increased extruder pressure improves porosity too.
Screwtech stuffers are built from high quality stainless steel, with an easy clean two-part vacuum chamber, separate seal housing and an oil filled gearbox with a water cooled jacket for long life at high temperature. Various sizes suit twin-screw and single-screw extruders. Get in touch with Screwtech Engineering to get your degassing back on track.
For more information on How do I improve vacuum degassing on an extruder? talk to Screwtech Engineering