How do I stop material rising up the vent port on my extruder?

Material rising up the vent port is one of the most common headaches on an extrusion line. You open a vent to get rid of air and moisture, and the melt decides it wants out too. Before long you have polymer in the vacuum line, a blocked port and a line that needs stopping.

It tends to happen for a few reasons. The barrel is running at a high fill level. Pressure is building in the section under the vent. The screw configuration is not quite right for the material. Or the vacuum is pulling hard enough to drag melt up with the gas. Often it is a mix of all four.

You can try to fix it by changing the screw configuration, dropping the fill level or easing off the vacuum. All of those cost you something, usually output or product quality. That is not much of a fix.

The more practical answer is a vent port stuffer. Screwtech Engineering supplies units with a self-wiping twin-screw design that pushes rising material back down into the barrel while gas carries on out. The screws clean each other as they turn, so the stuffer does not end up blocked itself.

With a stuffer in place, you can run at higher fill levels and keep a full vacuum on the vent without losing product. Screwtech units are built from high quality stainless steel, with an oil filled, water cooled gearbox for long life at high temperature.

Various sizes are available for twin-screw and single-screw extruders. If your vent is flooding, speak to Screwtech Engineering and get the problem sorted properly rather than working around it.

For more information on How do I stop material rising up the vent port on my extruder? talk to Screwtech Engineering