Rubber moulding shapes uncured rubber in a heated mould, where it cures (vulcanises) into the final part. Compression moulding presses rubber in an open mould and suits most parts; transfer and injection moulding push rubber into closed moulds for tighter, faster production. It makes seals, gaskets, grommets, bushes, bellows, mounts and rubber-to-metal bonded parts.
Quick facts
- Methods
- Compression, transfer, injection
- Materials
- NBR, EPDM, neoprene, silicone, natural rubber, Viton (FKM)
- Hardness
- About 30–90 Shore A
- Mould
- Steel mould, often multi-cavity
- Tolerance
- Looser than metal parts; standard classes for rubber
- Usually priced
- Mould cost once, then per piece
Which method
| Method | Best for |
|---|---|
| Compression moulding | Most parts, low to medium quantity, low mould cost |
| Transfer moulding | Rubber-to-metal parts, inserts, tighter sizes |
| Injection moulding | Large quantities, small precise parts |
Choosing the rubber
| Rubber | Good for |
|---|---|
| NBR (nitrile) | Oil and fuel |
| EPDM | Water, steam, weather, outdoor |
| Silicone | High and low temperature, food contact |
| Neoprene | General use, weather, moderate oil |
| Viton (FKM) | High temperature and chemicals |
What to send
- Drawing or sample with sizes
- What the part touches (oil, water, steam, chemicals) and the temperature
- Hardness in Shore A, and colour
- Metal inserts or bonding needed
- Quantity per order and per year
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Questions
- How much does a rubber mould cost?
- It depends on size and cavities, but compression moulds are usually much cheaper than plastic injection moulds.
- What is Shore A?
- A scale of rubber hardness: about 40 is soft like an eraser, 70 is a typical O-ring, 90 is very firm.
- What is flash on rubber parts?
- A thin skin of rubber at the mould parting line, removed by trimming, tumbling or cryogenic deflashing.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 29 October 2026.