Methods and apparatus for injection molding

摘要

A method of injection molding polyethylene terephthalate without being predried or with having an irregular-shape wherein a vent type injection machine is employed and the vent 8 is forcedly performed by vacuum suction within a range of a specified degree of vacuum, i.e. 50 to 150 torr (equal to 6666.1 SIMILAR 19998.3 Pa.) and/or at the same time the material is forcedly fed by a feed screw 4 having a specifically set revolution speed. According to the present invention, it is possible to provide an injection molding method in which an PET without being predried or with having an irregular-shape can be molded. The material feed is performed by detecting the rotational torque of the injection screw 7 in corresponding with the revolution speed of the feed screw 4 during material feed and setting the revolution feed of the feed screw 4 taking the flection point of the rotational torque as a guide.