Direct Pin Sensor Placement and Dynamic Viscosity Control in Micro-Moulds
Direct pin pressure sensing in micro-moulds compensates for melt viscosity drift by dynamically adjusting injection speed to hold precise shear rates.
Switchover Pressure Control
Meaning
Injection moulding process configurations transition the machine from velocity-controlled filling to pressure-controlled packing based on the cavity pressure. Processing engineers utilize switchover pressure control to ensure the polymer melt does not overpack the tool or cause flash at the parting line. This control method relies on a sensor in the mould cavity to trigger the change in machine action.
Process Stability
Traditional injection machines switch from filling to holding based on the position of the injection screw. This position-based method does not account for variations in the viscosity of the raw polymer melt or shifts in oil temperature. Using the cavity pressure instead of screw position to trigger the switchover compensates for these material and machine variations.
The moulding process remains consistent even when processing batches of resin with fluctuating melt flow rates.
Tool Protection
Overpressurizing the mould cavity can cause permanent damage to the expensive steel or aluminum plates. If the machine continues to inject polymer at high speed into a nearly full cavity, the resulting pressure spike can flex the clamp mechanism. This deflection leads to parting line wear and severe flashing.
Triggering the hold phase at a precise pressure limit prevents these destructive overpacking events.
Scrap Reduction
Consistent switchover timing ensures that every molded part has identical weight and dimensions. This precision is necessary for medical and automotive components with tight tolerances. Using this active feedback loop reduces the number of rejected parts during automated high-volume production runs.