| 摘要 |
PURPOSE:To obtain uniform plasticization, by successively repeating the retraction of a screw while rotating said screw in a kneading direction and the advance while rotating the same to the opposite direction during a stand-by period up to the next time injection. CONSTITUTION:When a metering process is initiated, the driving of a servo motor 15 is stopped while a servo motor 10 is driven to rotate a screw 1 to the direction opposite to a right-handed screw direction. The molding material supplied from a hopper is brought to a plasticized state by friction heat caused by the heat of a heater and the kneading action due to the rotation of the screw 1. In this case, pressure increases as the molten material sent into the leading end part of the screw 1 increases but the servo motor 15 is driven every when said pressure reaches definite pressure or more to rotate a worm 18 to a right- handed screw direction and the screw 1 is retracted to the direction opposite to that shown by the arrow A. That is, the screw 1 is rotated and retracted while difinite back pressure is applied and this driving is performed until the screw 1 exceeds a metering point. |
