Melt filter

In the field of plastics extrusion any kind of contamination in plastic melts is unacceptable for it not only affects the quality of the product but also impedes the operating process. Therefore it is essential to ensure a perfect filtration process without reducing the quality of the plastic melt. To define the size of a screen changer we need to know the extruder output, polymer and grade, shear rate, expected contamination level and target pressure lost. This data is fed into our latest computer modelling programme to indicate both the size of the screen changer but also the optimum flow channel dimensions. It clearly shows that the biggest part of the calculated pressure loss is produced by the filter element in front of the breaker plate. The inlet geometry of the screen changer interface to downstream components has to be designed to minimise shear the melt.