screen pack use notice
Since the extruder mesh screen is rusty, avoid moisture during storage, otherwise rust will appear in the extrudate. What's more serious is that the rust filter is easy to break and leak the filtered impurities. Therefore, the filter should be stored in a plastic bag or rustproof paper.
Do not place the exposed filter on the extruder head while the PVC material is being squeezed. This is because hydrochloric acid in the air near the die of the handpiece will corrode it. The best practice when extruding PVC is to install a fume hood above the die, and be sure to keep the spare filter away from it, or even put it in a freezer after bagging it.
When the protective plate is purged or cleaned, it is easy to cause reverse curling, which will damage the sealing surface and make the sliding surfaces not match, which will cause leakage. In this way, not only will the cleaning work be time-consuming, but the leaked molten material may affect the thermocouple value, damage the heater, and sometimes even cause a fire.
For a single-exhaust, two-stage extruder, if the back pressure at the filter screen becomes larger, the output of the second stage will be reduced, but the output of the first stage will not be affected. When the back pressure increased to approximately 2500 lb / in2 (1lb = 0.4536Kg, 1in = 25.4mm), the molten material from the first section began to leak into the exhaust hole slowly. To avoid this, be sure to replace the filter when the pressure is low. In addition, the gear pump behind the filtering device also has the effect of inhibiting the leakage of molten material into the exhaust holes.
If the screen pack large pieces of debris (such as paper), it will suddenly fail completely, which will cause the extruder pressure to peak quickly. Therefore, in order to prevent the above situation, a safety system such as a safety diaphragm, a safety pin or an alarm connected to a pressure gauge must be provided.
