The Influence Of Blow Molding Machine Filter On Plastic Extrusion Molding

During the extrusion process of the blow molding machine, the molten material is transported to the mold head through a filter screen. The filter screen filters the material and improves the mixing effect of the material. However, the filter can also cause fluctuations in the process, leading to an increase in back pressure and molten material temperature, and sometimes even a decrease.
The filter screen of the blow molding machine is fixed on a porous or grooved protective plate, which can form a seal between the blow molding machine and the mold head. The pressure generated by a clean filter is relatively small, possibly only 50-100lb/in2 (1lb=0.4536Kg, 1in=25.4mm). As the amount of impurities trapped in the resin on the filter increases, the pressure increases and the filter becomes clogged.
1, The filter screen will affect the temperature of the molten material
When replacing a clogged filter, the pressure may suddenly drop and the temperature of the molten material may also decrease, causing a change in the size of the product. In order to maintain the same size of the product, the screw speed of the blow molding machine can be adjusted, and the linear speed of the blow molding machine can also be adjusted.
When extruding circular products, these changes may not cause serious problems, but when extruding flat or irregularly shaped products, changes in the temperature of the molten material may affect the external dimensions of the product. For example, in a flat mold, colder molten material may make the center of the material thinner and the periphery thicker. This situation can be corrected through automatic or manual adjustment of the mold.
After the filter transformer, a gear pump is equipped to ensure the stable entry of molten material into the mold, which can prevent the occurrence of the above problems. However, the temperature changes of the molten material after replacing the filter still need to be resolved by adjusting the mold. Meanwhile, due to the susceptibility of gear pumps to damage from hard impurities, they also need to be protected by a fine filter screen.