Volumetric Areal Parameter Thresholds for Predicting Gate Wash Degradation
Volumetric areal parameters predict gate wear before profile roughness detects steel loss, preventing tool failure in glass-filled polymer injection molding.
Sub-Gate Land
Meaning
Narrow transition zone located between the end of a sub-gate and the entry into the part cavity regulates the resin flow and degating behavior. The sub-gate land provides a landing area where the runner system can be cleanly sheared away from the part during the ejection stroke. It is typically a short, flat section that controls the pressure drop.
Gate Separation
Automatic degating relies on the geometry of this specific section. As the mold opens or the ejector plate moves, the part is pulled away from the runner, and the gate snaps off at the land. If the land is too long, the gate may not break cleanly, leaving a protrusion or vestige on the part.
Proper sizing ensures that the break occurs exactly at the part surface.
Flow Regulation
Pressure loss across this small area influences the packing of the part. A very thin land can freeze off early, preventing the holding pressure from reaching the cavity and leading to sink marks. Adjusting the thickness and length of the land is a common way to fine-tune the filling of multi-cavity tools.
Tool Wear
Accelerated wear occurs when resin passes through the narrow gap. The land area often requires the use of hardened steel inserts to maintain its dimensions. Regular inspection ensures that the gate vestige remains within the quality specification.