Meaning
Managing the dynamic transition from velocity-controlled cavity filling to pressure-controlled packing, machine control algorithms govern the exact moment injection moulding machines switch from high-speed filling to hold pressure. Implementing precise switchover control prevents mold flashing and sink marks inside molded parts. Press controllers execute switchover based on screw position, hydraulic pressure, cavity pressure or fill time.
Position-based switchover remains common but fails to compensate for resin viscosity fluctuations across different material lots. Advanced switchover control utilizing in-mould cavity pressure sensors automatically adjusts transition timing to maintain consistent part weight despite melt index variations.
Transition Triggers
Screw position switchover triggers when the injection ram reaches a preset linear stroke distance. Hydraulic pressure triggers switch when system pressure reaches a critical cutoff threshold. Cavity pressure sensors trigger switchover precisely when the melt front reaches ninety-five percent cavity volume.
Defect Prevention
Late switchover causes overpacking, resulting in heavy parting line flash and tool damage. Early switchover causes short shots and sink marks due to inadequate cavity filling before pack pressure initiation. Dynamic switchover control eliminates dimensional drift caused by lot-to-lot resin viscosity shifts.
Sensor Integration
Piezoelectric cavity transducers deliver real-time pressure signals directly to press controllers. Closed-loop control circuits execute microsecond switchover adjustments to ensure uniform component density.
