Decoupled Injection Moulding Setup Principles for Technical Parts
Decoupled injection moulding decouples volumetric filling velocity from packing pressure to achieve tight tolerances and repeatable technical part production.
Decoupled I
Meaning
Injection moulding process control strategy separates the filling stage of the cycle from the packing stage based on screw position or volume. This methodology, known as decoupled i, allows the moulder to fill the cavity to approximately ninety-five percent volumetric capacity before switching to pressure control. By stopping the high-speed injection based on screw position rather than pressure, the process becomes less sensitive to variations in resin viscosity.
This separation protects the tooling from over-pressurization during the high-velocity filling phase.
Transfer Point
Screw position acts as the primary signal to trigger the transition to the pack phase of the cycle. When the screw reaches a predefined linear position, the machine drops the injection velocity and limits the hydraulic pressure. If viscosity shifts due to a higher regrind percentage, the machine still switches at the same volume, keeping the fill pattern stable.
This prevents flashes or short shots.
Pressure Limit
Peak hydraulic pressure during the fill stage can vary widely depending on the melt viscosity of the polymer. Because decoupled i relies on screw position, the actual cavity pressure at transition is not directly monitored or controlled by the machine. To prevent cavity damage, a hydraulic safety limit must be set above the normal fill pressure.
Process Control
Consistency of part weight improves when the high-speed injection stage is disconnected from the slower packing stage. The moulder adjusts the fill speed without affecting how the pack pressure compensates for volumetric shrinkage. This independence simplifies the optimization of cycles for multi-cavity moulds.
Decoupled Injection Moulding Process Optimization via Cavity Telemetry
Cavity pressure telemetry decouples polymer melt behavior from machine hydraulics, locking peak pressure to eliminate scrap and stabilize part dimensions.