Method and system for making a plastic film

A method of making a plastic film of a thermoplastic synthetic resin in a film-making system by extrusion from a die of an extruder, the method comprising the steps of:

• melting the plastic and extruding the melted plastic from the die as a tube or web;
• forming the extruded tube or web into a package;
• providing two reference parameters selected from the group comprised of material density, bulk density, dosage amount, melt density of the melted plastic, feed rate, and material leakage;
• during continuous operation of the system, measuring by respective measuring devices two input parameters different from the reference parameter and selected from the group comprised of melt pressure, extruder temperature, extruder speed, extruder torque, and melt temperature;
• determining from the measured input parameters respective output parameters corresponding to the reference parameters;
• comparing the determined output parameters to the reference parameters;
• and
• on deviation of one of the output parameters from the respective reference parameter, signaling an anomaly of the detected deviant output parameter by a visual or acoustic signal.