Injection molding machine, and method for adjusting a reverse rotation amount of a reverse rotation process in an injection molding machine

摘要

When a resin passage of a check ring (4) is opened, resin backflow occurs during time when an injection screw (1) is moved forward, and a reverse rotational force is applied to the screw (1) by resin backflow. On the other hand, when the resin passage is closed, there is no resin backflow and the reverse rotational force applied to the screw (1) is greatly reduced. Consequently, after completion of metering process and before injection process, the screw (1) is moved forward after the screw (1) has been rotated in reverse a predetermined amount to prevent resin backflow. At this time, a maximum value of the reverse rotational force applied to the screw (1) is detected. Until the detected maximum reverse rotational force reaches a reference value or less, the reverse rotation amount is increased sequentially and respective molding cycles are carried out. When the detected maximum reverse rotational force reaches the reference value or less (passage closure), the reverse rotation amount at this time is set as the reverse rotation amount for the reverse rotation process. By means of this operation, an optimal reverse rotation amount can be adjusted automatically.