A method for operating an injection-molding machine, including the steps: a) in a current injection-molding cycle, after an accepted-part reference injection-molding cycle learned in a learning phase: detecting a compound pressure change k.sub.1 relative to an accepted-part reference compound pressure p.sub.masse, ref during at least part of an injection phase of the current injection-molding cycle by measuring a current compound pressure p.sub.masse, act and comparing the current compound pressure p with the accepted-part reference compound pressure p.sub.masse, ref, b) determining a target mold internal pressure curve p.sub.wkz,soll (1) for a holding-pressure phase of the current injection-molding cycle, wherein for this purpose a mold internal pressure curve p.sub.wkz,ref (t) of the accepted-part reference injection-molding cycle is adjusted at least in dependence on the compound pressure change k.sub.1 detected in step a), and c) traveling the holding-pressure curve p.sub.masse, Hld, act (t) of the current injection-molding cycle in such a way that an actual mold internal pressure curve pwkz,act (0 of the current injection-molding cycle runs at least more closely along the target mold internal pressure curve p.sub.wkz,soll (t) than a mold internal pressure curve p.sub.wkz,ref(t) that is unchanged in comparison with the accepted-part reference cycle.

An injection apparatus includes (a) a barrel; (b) a nozzle at a front end of the barrel; (c) a screw in the barrel; and (d) a drive assembly including: (i) a housing having a front end coupled to the barrel; (ii) a spindle in the housing and fixed to the screw; (iii) a first motor in the housing and having a hollow first rotor through which the spindle passes. The first rotor is coupled to the spindle for driving rotation of the screw about the axis. The drive assembly further includes (iv) a second motor in the housing axially rearward of the first motor. The second motor has a hollow second rotor through which the spindle passes. The second rotor is coupled to the spindle for translating the screw along the axis in response to rotation of the second rotor relative to the spindle.

A method and system for adjusting melt pressure in an injection molding material that allows calculating a melt pressure of a molten plastic material to be injected and based on the calculated melt pressure and a desired melt pressure adjusting operation of an injection molding machine. This control of an injection molding cycle using the method and system of plastic melt pressure determination allows production of parts of increased quality and consistency.

In a method for operating an injection moulding machine in the absence of a backflow barrier, plastic melt is injected by a plasticising device into a cavity in a screw antechamber of a plasticising screw adapted to rotate about a longitudinal axis and to move translationally by a drive unit during an injection phase and a holding-pressure phase. A rotational drive of the drive unit is controlled such that a speed of the plasticising screw causes overlay of a backflow of the plastic melt from the screw antechamber back into screw threads of the plasticising screw by an opposing delivery flow as a result of a rotation of the plasticising screw due to a translational injection movement of the plasticising screw. A differential flow is established from the backflow and the opposing delivery flow and influenced at least during the injection phase by influencing the speed of the plasticising screw.

In a method for operating an injection moulding machine in the absence of a backflow barrier, plastic melt is injected by a plasticising device into a cavity in a screw antechamber of a plasticising screw adapted to rotate about a longitudinal axis and to move translationally by a drive unit during an injection phase and a holding- pressure phase. A rotational drive of the drive unit is controlled such that a speed of the plasticising screw causes overlay of a backflow of the plastic melt from the screw antechamber back into screw threads of the plasticising screw by an opposing delivery flow as a result of a rotation of the plasticising screw due to a translational injection movement of the plasticising screw. A differential flow is established from the backflow and the opposing delivery flow and influenced at least during the injection phase by influencing the speed of the plasticising screw.

An injection molding machine includes a cylinder; a screw; a rotary driving unit; a reciprocation driving unit; a pressure detector that detects a pressure of a molding material in front of the screw; a control unit that performs a first type of plasticizing process where the screw is moved backward to a predetermined position and rotated at the predetermined position to transfer the molding material forward to reserve the molding material in front of the screw, performs a first type of filling process where the screw is moved forward to inject the molding material reserved in front of the screw in the first type of plasticizing process from the cylinder to be filled in a mold unit, monitors the pressure in the first type of filling process by the pressure detector, and corrects the setting of the first type of filling process based on a monitored result.