Compression Moulding Basics

Elastomers and durometers can be moulded through compression moulding. During this technique, uncured rubber is inserted into the mould’s cavity, the mould is closed, and heat and pressure are applied. As a result, excess material fills the mould's overflow grooves, creating flashing. However, when the product is demoulded after curing is complete, and the mould is opened, the flashing is automatically removed.

Compression moulding is ideal for difficult-to-flow materials because it eliminates the need to push the rubber through sprues, gates, or runners. It is also the best method for working with expensive materials, moulding large parts, and running low-volume applications.

Compression moulding has a lower tooling cost compared to other moulding methods. Furthermore, it is the most cost-effective production method for smaller part runs. It's also great for large parts because the material is directly loaded into the mould cavity, so there's no weight limit on the parts that can be made.

However, compression moulding is less precise than injection moulding and generates more waste.

Furthermore, it has slower process times, which may be an issue when producing parts in higher volume, as the production rate will decrease while the part cost will increase.

In addition, compression moulding is not a suitable technique for manufacturing complex parts with depressions, side slopes, or small holes, and burrs must be manually trimmed. Another downside of compression moulding is that thermosetting plastic products with minor flaws may not be recyclable.

Some examples of compression moulding products include O-rings, grommets, plugs, and bumpers.

The rubber used for moulding often have the following properties:

  • It can be customised and manipulated into particular shapes and sizes.
  • It retains its waterproof properties.
  • It is crack resistant.
  • It maintains its shape under extreme pressure.

Contact Specialised Mouldings for details

There is much more to compression moulding than what is explained here. To discuss custom rubber moulding for your specific application, please contact a representative from Specialized Mouldings South Africa today.