Meaning
Injection molding process transition marking the switchover from volumetric filling speed control to pack pressure maintenance balances cavity packing against flash formation. Executing velocity to pressure transfer occurs at a designated cavity fill percentage, screw position or cavity pressure threshold. This switchover point prevents hydraulic pressure spikes, controls part sink marks and manages volumetric shrinkage during resin solidification.
The scope governs the fill-to-pack transition in closed molds, ending when packing pressure drops to zero during part cooling.
Switchover Timing
Transitioning from speed-controlled filling to pressure-controlled packing at ninety-five percent cavity volume prevents tool damage and part flash. Mismanaging velocity to pressure transfer causes short shots or excessive part strain depending on whether the transfer occurs early or late. High-precision medical connectors and optical housings require repeatable switchover timing to maintain tight dimensional tolerances.
Precise transfer calibration guarantees consistent part mass across long production runs.
Spike Suppression
Timely velocity to pressure transfer prevents hydraulic momentum from generating sudden pressure peaks that force mold parting lines open during injection.
Margin Audit
Technicians calibrate screw position transducers and cavity pressure sensors during mold trials to establish the velocity to pressure transfer window. Setting the transition point based on machine hydraulic pressure rather than cavity melt position introduces weight variations when raw material viscosity fluctuates. Calling a process qualified without testing switchover tolerance across material lot changes leads to high scrap rates during commercial runs.
Verifying cavity pressure curves during pilot testing establishes acceptable process windows for continuous manufacturing operations.
