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Effect of Extruder Filter on Plastic Extrusion

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 / in2 (1 lb = 0.4536 kg, 1 in = 25.4 mm). As the pressure increases, the amount of impurities trapped in the resin on the filter increases, clogging the filter.
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The filter affects the temperature of the molten material. When changing a clogged filter, the pressure drops suddenly and the temperature of the molten material may drop, causing the product to change its dimensions. In order to maintain the same size of the product, the screw speed of the extruder can be adjusted, and the linear speed of the extruder can also be adjusted. These changes may not cause serious problems when extruding a round product, but variations in the temperature of the melted product may affect the overall dimensions of the product when the flat or irregularly shaped product is extruded. For example, in a flat die, colder melts may thin the center of the sheet and thicken the periphery. This can be corrected by automatic or manual adjustment of the mold.

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