Meaning
An injection molding control algorithm calculates the mathematical integral of the injection pressure over the filling phase to monitor and adjust the transition to the holding phase. This closed-loop control method, called pressure integral control, governs the consistency of melt delivery by compensating for shot-to-shot viscosity variations. The strategy applies to precision molding of technical parts and is unnecessary in simple molding applications where dimensional tolerances are wide.
Process Stabilization
The control system continuously calculates the area under the pressure-time curve during the fill stroke. Pressure integral control adjusts either the injection speed or the switchover point in real time to maintain a constant energy delivery to the polymer melt. This correction prevents the process from drifting when melt viscosity fluctuates.
Switchover Optimization
Traditional screw-position switchover ignores changes in raw material viscosity and melt density. When the viscosity rises, the mold is filled with less material at the same stroke position, causing short shots. This feedback loop adjusts the transition point to ensure that the cavity receives the correct volume of melt.
Quality Consistency
Dynamic compensation reduces the variations in part dimensions and weights during long production shifts. Scrap rates caused by start-up temperature transitions and regrind usage are minimized because the controller adapts to the changing flow resistance of the polymer. This control keeps the molding process centered within the target specification window.
