Abstract: A control method of an injection molding machine includes the steps of advancing a screw 2, injecting and filling the resin in a barrel cylinder 3 into a mold 4 to fill the mold, and then applying a predetermined holding pressure to the resin in the mold 4. The control method further includes the steps of performing an injecting and filling by using an injection cylinder 5 having a double-rod piston 6 which can advance and retreat the screw 2, and then controlling the injection cylinder 5 by a controlling signal Dc including a predetermined alternating current signal in such a manner that the screw 2 is reciprocated in a longitudinal direction as a center with an advance finish and. stop position Xs and a position at which the screw is moved so as to retreat by a predetermined distance from the advanced finish and stop position Xs. Thereby, the mold failure such an overpack and a burr is eliminated.

Abstract: A pressure detecting apparatus of an injection molding machine is utilized for always keeping an accurate zero adjustment point and accurately and precisely detecting pressure without being influenced by temperature drift. The pressure detecting apparatus includes pressure sensors for detecting the oil pressures of hydraulic cylinders such as injection cylinders. Correction value computing sections are provided for obtaining detected pressure values according to the outputs of the pressure sensors in a period in which the oil pressures theoretically become zero as correction values. Correction value storing sections are provided for storing the obtained correction values. Pressure correcting sections are provided for correcting the detected pressure values by the correction values according to the outputs of the pressure sensors at a time of pressure detection.