Injection Molding SampleWe learned last month that selecting the optimal gate size and location is vital in the creation of any molded part. However, that is just half the story. Just as pivotal to the success of the design is the type of gate that is used.

There are actually four main types of gates that are frequently used when molding parts. Edge gates are often popular since they are fairly simple and cost effective, but may not always be the best choice. Here is a brief description of some gating options that will help you customize your design and really take your part to the next level.

Edge Gate • Suitable for medium and thick sections
• Used on multi-cavity two plate tools 
• Gate located on the parting line and the part fills from the side, top or bottom
DOWNSIDE: leaves “vestige” at gate location which should be trimmed with a secondary process
Submarine Gate • Used in two-plate mold construction
• As parts and runners are ejected, the gate is sheared at the part
• Tunnel can be located either in the moving mold half or in the fixed half
• Sub-gate is often located into the side of an ejector pin on the non-visible side of the part when appearance is important
Sprue Gate • Recommended for single cavity molds or for parts requiring symmetrical filling
• Suitable for thick sections where holding pressure is more effective
• A short sprue is favored, enabling rapid mold filling and low-pressure losses.
• A cold slug well should be included opposite the gate.
DOWNSIDE:  a gate mark is left on the part surface after the runner (or sprue) is trimmed off.

We hope this gives you some ideas for your next molding project. If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.