Meaning
Systematic testing procedure used to determine the exact moment the polymer flow path into a mould cavity solidifies. Performing gate seal validation ensures that the injection holding pressure is applied for the correct duration. If the gate has not sealed, polymer can flow back into the runner system when pressure is released.
Freeze Point
Progressive cooling of the narrow gate channel eventually restricts any further material transfer into the cavity. The gate seal validation process identifies this transition by monitoring the mass of the moulded parts over a series of test runs. Moulders plot the part weight against hold time to locate the plateau where weight ceases to rise.
This method avoids premature gate release and minimises the risk of backflow.
Weight Metric
Once the plateau is reached, further increases in holding time yield no change in part weight. A typical test increments the holding time by one second per shot. This straightforward data collection provides a clear visual curve for process setup.
Defect Prevention
Premature release of hold pressure leads to sinking, voids and weight variation in the finished parts. Excessive hold time past the seal point wastes energy and increases cycle times without adding value. Standardising this measurement stabilizes the production of high-precision components.
