Dynamic Cavity Pressure Integral Correlation with Part Dimensions in Injection Moulding
Dynamic cavity pressure curve integration over hold time governs volumetric polymer density and predicts final part dimensions before tool ejection occurs.
Packing Pressure Integral
Meaning
A process monitoring metric in injection moulding represents the cumulative pressure exerted during the packing and holding phases of the cycle. Calculated as the area under the pressure-time curve from the moment of transition until the end of the holding stage, the packing pressure integral measures the total force applied to compress the polymer melt. This metric helps ensure part weight consistency and prevents shrinkage or warpage in the finished component.
It is used to monitor the consolidation of the plastic in the cavity as the gate freezes.
Cavity Consolidation
During the packing phase, additional polymer is forced into the mould cavity to compensate for thermal contraction. This consolidation requires sustained force, which is captured by the pressure measurement. If the integral value is too low, the part will lack sufficient material, resulting in sink marks.
Part Consistency
Production lines utilize this metric to identify weight variations across different shots. The packing pressure integral acts as an indicator of how much polymer was forced into the cavity during each cycle. When this value remains within narrow limits, the moulder is assured that the parts will have uniform dimensions and mechanical properties.
Gate Freezing
Establishing the timing of gate solidification determines the limit of the packing and holding phase. Once the polymer in the gate freezes, pressure in the cavity can no longer be influenced by the machine screw, and the integral curve flattens out. Tracking this transition helps processors optimize the holding time to avoid wasting energy and cycle time, which reduces the overall cost of production.