Abstract: A method of influencing a backpressure length and/or a screw return speed in an axially extending plasticizing cylinder of a plasticizing unit for an injection moulding machine including a plasticizing screw arranged displaceably and rotatably in a cylinder bore of the plasticizing cylinder. Metering of plastic granulate fed to the plasticizing unit is carried out in dependence on the desired backpressure length in the plasticizing unit, and the plasticizing unit is operated in underfed mode.

Abstract: An injection unit includes an injection cylinder and a plasticizing screw in the injection cylinder. The plasticizing screw is rotatable about a longitudinal axis for plasticizing plastic raw material and is movable linearly along the longitudinal axis for injecting molten plastic raw material. The injection cylinder has an infeed and plasticizing zone for the plastic raw material with a circular-cylindrical inner wall with a constant diameter along the longitudinal axis, a metering zone in front of the infeed and plasticizing zone along the longitudinal axis in the injection direction with a circular-cylindrical inner wall with a constant diameter along the longitudinal axis, and a nozzle head in front of the metering zone in the injection direction with a nozzle-shaped inner wall. The diameter of the circular-cylindrical inner wall of the metering zone is smaller than the diameter of the circular-cylindrical inner wall of the infeed and plasticizing zone.

Abstract: A method of influencing a backpressure length and/or a screw return speed in an axially extending plasticizing cylinder of a plasticizing unit for an injection moulding machine including a plasticizing screw arranged displaceably and rotatably in a cylinder bore of the plasticizing cylinder. Metering of plastic granulate fed to the plasticizing unit is carried out in dependence on the desired backpressure length in the plasticizing unit, and the plasticizing unit is operated in underfed mode.