Abstract: A nozzle internal resin pressure feedback control system has a mold internal pressure sensor for measuring a mold internal resin pressure as a measured mold internal pressure value. The measured mold internal pressure value is fed to the nozzle internal resin pressure feedback control system, and a nozzle internal pressure preset value in the nozzle internal resin pressure feedback control system is changed in accordance with a difference between the measured mold internal pressure value and the mold internal pressure preset value.

Abstract: A control method for an injection molding machine comprises the steps of measuring a density of a molten resin in a heating cylinder, controlling a stroke of an injection screw in an injection process by feed forward control based on the measuring step, and controlling an operating parameter of the injection molding machine based upon the measuring step.

Abstract: A control method for an injection molding machine comprises the steps of measuring a density of a molten resin in a heating cylinder, controlling a stroke of an injection screw in an injection process by feed forward control based on the measuring step, and controlling an operating parameter of the injection molding machine based upon the measuring step.

Abstract: A nozzle internal resin pressure feedback control system has a mold internal pressure sensor for measuring a mold internal resin pressure as a measured mold internal pressure value. The measured mold internal pressure value is fed to the nozzle internal resin pressure feedback control system, and a nozzle internal pressure preset value in the nozzle internal resin pressure feedback control system is changed in accordance with a difference between the measured mold internal pressure value and the mold internal pressure preset value.

Abstract: A back-flow prevention apparatus includes a screw which includes a metering portion and a screw head; a seal ring which is removably disposed on a rear portion of the screw head and which has a first resin passageway formed therein; a back-flow prevention ring which is disposed on a front portion of the screw head in such a manner as to be rotatable with respect to the seal ring and which has a second resin passageway formed therein; and a drive unit for selectively rotating the screw in a regular or reverse direction. A first positioning mechanism is disposed between the screw head and the seal ring and adapted to position the seal ring at a predetermined position with respect to the screw head.

Abstract: A screw of a screw-in-line type plasticizing device of an injection molding machine has a cylindrical main part and a spiral screw flight on the main part. A portion of the screw flight of the screw facing a resin supply port has a parallelogrammic axial sectional shape which is inclined towards the discharge end of the screw.

Abstract: A screw head is composed of a cone portion, a tapered portion formed behind the cone portion and a narrow portion formed behind the tapered portion. A counter-flow stopper ring is provided around the narrow portion so that an annular resin passage is formed between the counter-flow stopper ring and the narrow portion. The tapered portion of the screw head has a plurality of circumferentially spaced grooves. The sectional area of each groove decreases from the inner circumference toward the outer circumference of the tapered portion. The grooves are so formed that the resin flowing through the grooves creates a force which pushes the counter-flow stopper ring backward, the ring being moved forward by forward flow of resin caused during backward movement of the screw. Thus, the grooves help maintain a gap between the counter-flow stopper ring and the screw head.