Rubber mouldings are something that we are around every day without ever really noticing. They are used for a vast range of commercial, industrial and domestic purposes, such as weather, dust and moisture seals for indoor and outdoor lighting, vibration mounts for vehicles, and gaskets to make doors and window glazing watertight.
Practically every industry requires moulded rubber products, including industries such as construction, manufacturing, lighting, HVAC, automotive, defence, and the rail industry.
The rubber moulding process
The manufacturing process of moulding rubber involves placing granulated raw rubber compound into the cavities of a pre-heated mould, which is modified depending on the desired shape of the component required, allowing rubber to be used to create a wide range of products, including small and large moulded parts and highly intricate designs.
To reduce waste material, the amount of raw compound used will differ depending on the desired shape and size of the component to be produced. To make sure that the right amount of material is used, it will be weighed before it is added to the cavities of the mould. Once filled, the mould is closed and heat and pressure are applied to the granular material. The heat causes the material to melt and bond together, in order for it to solidify in the desired shape of the component.
The amount of time needed to complete the moulding process depends entirely on the specific material used, the moulding temperature, and the size of the desired component.
Compression moulding or injection moulding
The two most common methods for rubber moulding are compression and injection moulding:
- Compression moulding – raw rubber granules are placed into a preheated mould, before it is closed and pressure and heat is applied.
- Injection moulding – molten rubber compound is injected into a closed moulding at a high pressure in order to form the intended shape.
In order to choose which moulding process is best suited for your requirements, it’s important to think about some of the pros and cons.
One of the key benefits of compression moulding is that it is a fairly simple process, with the raw material simply being placed directly into the pre-heated mould for pressure to be applied. However, though the process is simple, it can produce highly intricate rubber moulded components when compared with other moulding processes.
Compression moulding is well suited to producing large rubber mouldings that require larger volumes of raw rubber compound. In contrast, injection moulding limits how much raw rubber can fit the injection barrel used to fill the mould.
If you are seeking short production runs of moulded rubber parts, compression moulding is certainly a good choice as the costs involved, including the manufacture of new tooling, are relatively low, compared to other moulding processes.
The injection moulding process has multiple advantages, including producing extremely consistent results, helping reduce quality failure considerably. There is also very little waste material produced, or need for trimming or finishing before components are ready for sale or use.
For long runs of rubber moulding production, injection moulding is a great choice, as it can produce parts on faster cycles than compression moulding, so products can be manufactured in mass in a relatively short time period. Whilst tooling for injection moulding is more expensive, it’s important to consider that mass production helps to achieve return on the tooling investment, and that thousands upon thousands of parts can be moulded before tooling maintenance is required.
Moulding advice
To make the correct choice of moulding processes and material selection to fulfil your unique specifications, it’s important to seek advice from rubber conversion experts. CB Frost specialise in manufacturing moulded rubber components, gaskets and extruded parts for all major industries and can help you to make informed decisions.