Method of injection molding polyethylene terephthalate

摘要

A method of injection molding whereby a polyethylene terephthalate (PET) without being predried or with having an irregular-shape is fed by a feed screw from a material feeder to an injection cylinder and plasticated by an injection screw. The rotational torque of the injection screw is detected in correspondence with the revolution speed of the feed screw during material feed, and a flection point of the rotational torque is determined. The feed screw is operated at a revolution speed within a range around the flection point of the rotational torque to provide a stable feed rate of the PET and to avoid difficulty in rotating the injection screw.