The drying hopper is used to remove moisture from the plastic raw material. If the plastic raw material is fed into the injection molding machine without drying, the moisture contained in the raw material will become bubbles after the raw material is dissolved. After injection, air bubbles will appear on the surface of the preform, which increases the scrap rate of the preform, resulting in the loss of final production. Therefore, it is very necessary to dehumidify before injection molding. PET raw materials must be heated and dried at a high temperature of 175 ° C in a drying hopper for 5 to 6 hours before injection molding. After drying, the preforms produced are free of blisters and have a better surface finish. An additional benefit of dehumidifying in the hopper is that it reduces the possibility of contamination of the material during transport from the central dryer to the machine hopper.

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