An introduction to the rubber injection moulding process

Unlike the use of plastic within injection moulding, using injection moulding to create parts made from rubber can be a highly complex activity. The issues behind the behaviour of the molten rubber, coupled with considering how it will cool and how the stresses involved with the moulding process can be minimised, all help to make for a highly specialised and difficult activity.

Why injection mould?

Generally speaking, injection moulding is a favourable way to produce parts when they need to be delivered consistently and with great volume.

New technology such as 3D printing has been used for a good few years when prototyping parts. Whilst a 3D-printed prototype can give a great idea of what a part will look like, an injection moulded prototype can be manufactured in a similar manner to the finished part and can also be made from the same material, bringing additional credence to the prototyping process.

The process explored

First, a mould needs to be prepared that has the exact dimensions of the part to be manufactured. Then, the rubber injection moulding companies would use a screw feeder system to insert the exact amount of uncured rubber into the machine. This rubber is then transferred to a heated barrel to be melted slowly.

Once the rubber is heated to the melting point, it flows gently into the mould, filling all of the cavities evenly. Once the mould is filled, it is then cooled slowly in order for the new part to solidify and cure.

After curing, the part can be removed from the mould and the process can begin again.

Why use this process?

In manufacturing terms, injection moulding is a process that ends up with very little waste. As the correct amount of rubber is heated, injected into the mould and cured, intricate and custom shapes can be produced while wasting almost no raw materials.

Some of the disadvantages of injection moulding include the high startup costs that are involved, and this may well not be the most cost-effective process if high volumes of products are not going to be produced.

As a very specialised and versatile process able to produce high quality and intricate parts consistently, injection moulding can work just as well with rubber as it can with plastic.

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