How to Use a Valve Gate for Injection Molding

IMGP0442c-smallInjection molding remains to be one of the best ways to increase production for just about any industry. Plastic is an inexpensive material that is used in everything from the automotive to fashion industries, all while offering a high quality product. With that being said though, traditional injection molding does usually have a downfall. The plastic that is pushed out the nozzle of the injection barrel usually has a run off. This is what results in the hanging plastic tags on many different products. Not only is this not attractive but it can reduce the strength of the plastic as well. Due to this, it is necessary to be able to prevent this drooling effect an injection nozzle creates. With the help of valve gating, the liquid plastic is controlled and cut off whenever possible, providing a clear cut to the plastic and allowing the production to avoid the plastic tagging that is so commonly associated with injection molding.

How to Use a Valve Gate

The title valve gate describes the purpose of this equipment perfectly. Prior to the creation of a valve gate, the liquid plastic would continue to flow out, even after the injection mold is full. This causes the plastic strand to hang from the mold to the nozzle so, when the plastic is hardened, there is a piece of this tag still hanging form the finished product. To avoid this sort of dripping effect, a valve gate is used to instantly cut off any sort of flow of plastic out the nozzle. The injection molding is programmed as to how much plastic is needed to fill the mold. Once this specific amount passes through the barrel of the injection molding equipment and out the nozzle, the valve gate closes instantly, preventing any more plastic from passing through. As the plastic flow is cut off right at the point of the valve, there is no plastic remaining to cause the hanging plastic tag.


By avoiding the hanging plastic tag there are several different benefits. First, it improves the appearance of the final product and it also improves durability as the hanging tag is no longer present to reduce the strength and durability of the final product. Lastly, it saves the production money on every single finished item and, by the end of a production run, it may save the business thousands of dollars in saved plastic.

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