In injection molding, each cavity in a mold must contain a small opening called a gate, which allows hot plastic to enter the cavity before passing through and around its internal features until filled.

Design side gate is the most generally of mold design, and used well in multi-cavity mold. Its shape is a rectangle or semicircle, and placed at side of the molded product. It can use for a product with small side or middle thickness because gate structure is easy and don need high quality.

This article looks at six of the most common gate types used in injection molding: edge gates, tab gates, direct/sprue gates, hot tip gates, pin gates, and sub gates.

The gate location on an injection molded part leaves a “witness” where the part is separated from the runner system. This is considered an appearance defect and is typically hidden in an inconspicuous location on the part.

Small gates provide a better appearance, but require longer mold time or higher pressure to fill properly. Higher cavity pressures cause more stress to be molded into the part. … In plastic injection molding, if gate size is inadequate the flow rate of the molten resin will be restricted as it tries to move through.