Meaning
Machined reference surfaces establish the depth offset of a runner feed orifice relative to the mold cavity wall. Precision tool inspection measures gate land recession by comparing the position of the gate land edge against the adjacent cavity surface profile. Recessing the gate land into the mold steel creates a small residual nib that remains below the nominal flush surface of the finished plastic part.
This geometry prevents trimmed gate burrs from protruding beyond part design envelopes during final assembly. Proper pocket geometry protects functional sealing surfaces and mating faces from aesthetic defects. Automated trimming operations benefit from consistent gate break points provided by structured land depth offsets.
Shear Control
Short land lengths reduce localized viscous heating as molten polymer passes from the runner into the cavity. Incorporating gate land recession narrows the restrictive land area without compromising the structural wall strength around the runner drop. Polymer melt degradation decreases when shear heating remains within resin processing windows.
Proper land relief lowers total injection pressure requirements during high-velocity cavity filling.
Submarining Mechanism
Submarine and cashew gates utilize recessed pockets to shear the runner automatically during part ejection. Correct gate land recession allows the tunnel gate to break cleanly beneath the part surface, preventing surface vestige pulling.
Dimensional Offset
Tool wear from processing glass-filled compounds increases gate orifice dimensions over time, altering the effective gate land recession. Micro-edm wire erosion restores accurate gate geometry during mold refurbishment.
