For those of us who are new to injection moulding, we at NICE Rapid thought that we would describe some important aspects of the moulding process and some of the terms that you might have heard being discussed. This week we will be talking about ‘gates’ and their different types.

What are gates, why are they important and where should we put them? The term ‘gate’ is used to describe the area of the mould into which the liquid resin flows. This is something that will be visible on the final product, so it is important to ensure that it is either in an inconspicuous place or is sited where it is of little detriment to the cosmetics of the part. Obviously, in parts that are used in car manufacturing or something similar, this is dependent on where the part will be located. A part visible to the consumer will have to be produced so that the gate is hidden, whereas if a part is located within the bodywork and is not visible to the consumer, this will not be of importance. The location of the gate also impacts on the structural integrity of the finished part and this is of paramount concern if the part is safety critical or of high cost.

Below is a description of the types of gates you may find on an injection moulded part:

Sprue: This gate is easy to locate, but there is a high stress area around the gate and it is required to be manually trimmed, adding time and cost to the production process. It is suitable for large parts and because the gate can be easily placed, it is able to be located where there is less cosmetic impact on the part itself.

Side: This type of gate is easier to locate and remove than a Sprue Gate, but still cannot be trimmed automatically, however, it can be unsightly and this should be taken into consideration with cosmetically delicate parts. It can be used for many types of part, but is unsittable for barrel-shaped designs due to its location.

Point: This gate is able to be located in many positions and can be removed from the part automatically. There is lower stress around the gate itself and it leaves a smaller footprint on removal than the other types. Downsides are that the gate is fairly complicated to incorporate into the initial design and it requires a high injection pressure to achieve the best results.