Method for controlling injection molding machine capable of reducing variations in weight of molded product

摘要

A synchronization ratio S of a rotation speed of a screw, in which the position of a flight thereof does not apparently move relative to a backward speed R of the screw, is defined as 100%. The screw is driven backward while being rotated. A rotation speed R of the screw during the backward movement is given by multiplying the rotation speed R, which is expressed by the equation, R = backward speed V/pitch P of the flight, by an arbitrary synchronization ratio Sx, wherein when the synchronization ratio S is less than 100%, the screw is rotated more slowly relative to the backward speed V of the screw, so that a resin in the heating cylinder tends to be dragged backwards and wherein when the synchronization ratio S is 100% or more, the screw is rotated faster relative to the backward speed V of the srew, so that the resin in the heating cylinder tends to be fed forward to the screw.