Extruder screens are used to filter impurities from molten plastic during the extrusion process as well as creating back pressure within the extruder barrel to assist in improving the mix of polymer, masterbatch and other compounds where coloured compounds are involved.

Extrusion applications where screens are used include

• Plastic reclamation and recycling
• Profile Extrusion
• Blown Film

Typically manufactured using Mild Steel or Stainless Steel meshes, the screens can be cut using either a dedicated press tool, circle or laser cutting methods to be supplied as

• Single Layer Filters
• Spot Welded Packs
• Multi or single layer Rim Packs with either Aluminium or Stainless Steel enclosures

Regardless of screen format, specifications can be in Plain Weave or Hollander Weave also referred to as Dutch Weave.

The use of coarser filter screens against the screen changer breaker plate helps to withstand the pressures generated during the extrusion process and prevent screens from bursting.

Single Layer Filter Screens

Screens of one layer are typically used within polymer reclaim, blown film or plastic profile extrusion applications. Screens are used to filter out impurities within the raw material or to increase the back pressure within the extruder barrel to improve masterbatch dispersion within the barrel.

Multiple single layer screens can be used, and inserted into the screen changer’s breaker plate individually, thus allowing flexibility of different filtration rates from one polymer batch to another.

Spot Welded Packs

Layers of individual filter screens are assembled to customer requirements and secured together by spot welding at various locations close to the circumference. Spot welded packs are generally, but not always, layered with the coarser mesh grades on the outsides, leading to the finer specification in the centre. Customers can opt for their own preferred selection of specification layers including packs assembled as mirrored from the inside out on both sides. By having a mirrored screen pack, the risk of inserting the screens back to front is eliminated.

Rimmed Pack Filter Screens

In addition to screens being supplied in pre-assembled layers, an outer rim / enclosure of Aluminium or Stainless Steel can be applied to the circumference.  Such packs are found to be used on older extruders where the breaker plate ay contain surface irregularities which could potentially result in seepage or polymer by-passing a conventional mesh screen pack. Once inserted into the breaker plate recess, the outer rim forms itself into the peaks and troughs of the solid land area around the breaker plate’s outer edge and creates a seal to reduce or eliminate polymer containing contaminant from by passing the screen.

If you need an emergency service at short notice please call us.