During the extrusion of the extruder filter, the molten material is fed through the screen to the mold. Filter to filter the material, and can improve the mixing effect of the material. However, the filter can also make the process fluctuations, resulting in back pressure and melt temperature rise, and sometimes reduce. The extruder screen is secured to a perforated or slotted guard plate to seal the extruder and die. The pressure generated by a clean filter is small, probably only 50 to 100 lb