The gate serves as the entrance to the cavity and should be designed to permit the mold to fill easily. A cavity can have more than one gate. Gates should be small enough to ensure easy separation of the runner and the part but large enough to prevent early freeze-off of polymer flow, which can adversely affect the consistency of part dimensions. A variety of gate designs and locations are shown below:

An edge gate located below the parting line or molded surface.

Tunnel Gate

A restricted opening between the runner and molded part. Normally used with thin wall parts.

Restricted gate

A common gate located in the sidewll of the part to prevent restriction of resin flow. Normally used with multi-cavity, two-plate molds.

Edge gate

Used for melt orientation when a large volume is needed for mold fill. The tab helps avoid surface splotches due to high shear, direct gating, or jetting.

Tab gate

Recommended for single cavity molds requiring symmetrical filling. Usually used with circular parts.

Sprue gate

A long, shallow, rectangular edge gate.

Flash gate

A system used when concentricity and a smooth interior surface are important. Can be used in multi-cavity molds.

External ring gate

A System used with large circular parts when concentriciy and smooth outer surface are required. Can only be used with single-cavity molds.

Internal Ring Gate