Multi Cavity Mold Gate Risk Assessment and Statistical Process Control Verification
Multi cavity gate verification requires cavity-isolated statistical capability analysis and matched pressure integrals to prevent dynamic fill defects.
Injection Velocity Profile
Meaning
Programmed multi-stage ram speed sequences control the volumetric flow rate of molten polymer as it fills an injection mold cavity. An injection velocity profile regulates melt front velocity across changing cavity cross-sections, gate transitions, and runner networks to prevent flow hesitation and surface imperfections. The control boundary governs the filling phase from screw forward movement start up to the velocity-to-pressure changeover point, where the packing phase begins.
Filling Dynamics
Mold cavities with alternating thin and thick sections require variable screw advancement speeds to maintain a constant linear melt front speed. Slow initial injection through narrow gates prevents shear degradation, jetting, and gate blush. The machine controller ramps velocity upward once the gate is cleared to fill broad cavity spaces before polymer freezing occurs.
A controlled deceleration just before cavity completion prevents dynamic pressure spikes and mold flashing.
Process Validation
Process setups optimized on single-cavity prototype tools fail when transferred to multi-cavity production tooling with complex runner balances. Relying on machine position alone without monitoring cavity pressure curves produces inconsistency across resin viscosity batches. Early changeover from velocity control to packing pressure causes under-filled short shots.
Late changeover generates severe internal stresses and part sticking in the mold cavity.
Sensor Control
Transducers mounted behind ejector pins or inside cavity walls capture real-time melt arrival times across the tool. Closed-loop hydraulic and all-electric injection units adjust screw speed dynamically to replicate target pressure fill curves. Consistent velocity profiles yield uniform molecular orientation and reduce anisotropic part shrinkage across long production campaigns.
Statistical monitoring of velocity-to-pressure changeover position confirms process repeatability on every injection cycle.