Different Gates for Plastic Injection Molds
Apr 19, 2021

During mold design, it’s important to choose a proper gate type for your application. There are many different gate designs available based on the size and shape of your part. Below are some the most popular gate designs.

1. Edge gate:

The Edge Gate is the most common gate design. It’s located on the edge of the part and is best suited for flat parts. Edge gates are very suitable for medium and thick sections and can be used for multi-cavity two-plate molds. This gate will leave a scar on the parting line.

2. Sub gate

The sub gate is the only automatically trimmed gate. Ejector pins will be necessary for automatic trimming of this gate. Sub gates are quite common and have several variations such as banana gate, tunnel gate and so on. The sub gate allows you to make the gate away from the parting line, giving more flexibility to place the gate at an optimum location on the part. This gate leaves a pin sized scar on the part.

3. Hot tip gate

The hot tip gate is the most common of all hot runner gates. Hot tip gates are typically located at the top of the part rather than on the parting line and used for round or conical shapes where uniform flow is necessary. This gate leaves a small raised nub on the surface of the part. Hot tip gates are only used with hot runner systems. It unlikes cold runner systems, the plastic injection molds is ejected into the mold through a heated nozzle and then cooled to the proper thickness and shape in the mold.

4. Direct gate

The direct gate is a manually trimmed gate that is used for single cavity molds of large cylindrical parts that require symmetrical filling. Direct gates are the easiest to design and have low cost and maintenance requirements. The disadvantage of using this type gate is the gate mark left on the part surface after the runner (or sprue) is trimmed off.

5. Fan gate

A fan gate is a wide edge gate that used in flat or thin wall thickness products. It permits rapid filling of large parts through a large entry area.

6. Tab gate
Tab gate is typically employed for flat and thin parts, to reduce the shear stress in the cavity. The high shear stress generated around the gate is confined to the auxiliary tab, which is trimmed off after molding.

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