Method, apparatus and press for injection moulding of plastic material

A method for injection moulding of plastic material for joint-moulded components of a same family, comprising:

• introducing the plastic material into multiple cavities of a single family mould in a filling step followed by packing the plastic material introduced into the single family mould during a subsequent packing step, wherein the filling step is performed by actuating a plurality of injectors in a sequential or cascade manner, the plurality of injectors being connected to one hot runner or distributor, which is connected to one injection press, the plurality of injectors each provided with respective valve pins movable between a closing position and an opening position in a controlled fashion with respect to at least one among position, velocity and acceleration;
• supplying the plastic material to the one distributor by the one injection press comprising a screw axially displaceable by an actuator, wherein the plastic material supplied to the distributor is at an injection pressure, and wherein said injection pressure is detected at an outlet of said screw upstream of an inlet of said distributor;
• and
• maintaining the injection pressure supplied to the one distributor substantially constant at an inlet to each of the injectors by said actuator from a start of the filling step up to an end of the plastic material packing step, whereby the injection press through variations of position and advancement velocity of the screw, automatically reacts to openings of each of the plurality of injectors and resulting pressure excursions based on at least said detected injection pressure to always provide the substantially constant injection pressure in the distributor such that controlling the injection pressure and/or flow rate flowing out from one of the plurality of injectors does not affect control of pressure and/or flow rate flowing out from the other injectors of the plurality of injectors;
• wherein said substantially constant injection pressure is a maximum pressure, which is a peak pressure regulated by the injection press during each molding cycle;
• and
• wherein one or more injectors of the plurality of injectors are associated to each of the cavities of the single family mould, wherein one or more of the cavities of the single family mould have different shapes and/or sizes and/or volumes, and wherein respective injectors associated to different cavities of the single family mould are controlled to provide different packing pressure and/or flow rates while the substantially constant injection pressure in the distributor is maintained.