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Where a specific moulding profile is required, we apply our extensive experience to help you design to achieve the most reliable and cost effective solution.

We are currently manufacturing bespoke seals such as:

  • Lip seals / U-seals / V-seals
  • Symmetrical seals
  • Quad rings
  • Moulded gaskets
  • Bespoke radial seals

Tolerances for moulded parts

Moulded seals are subject to changes in their geometry during vulcanization. These changes should be allowed for when designing. The greater the degree of accuracy demanded, the closer the control which must be exercised during manufacture.


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All rubber shows some shrinkage when cooled after moulding, and allowance for this is made in the mould design. The amount of shrinkage is dependent on rubber type. Moulds are made in various ways depending on the type of product and accuracy demanded. Superior recommend the use of ISO 3302-1 Class M2 tolerance for high-quality precision mouldings (see table below). In compression moulding more rubber is used than is required to fill the cavity, and the excess is flashed. This flash can prevent the mould sections from fully closing and thus affects the finished part dimensions. However, for injection and transfer moulding all dimensions can be considered as fixed.

To find out more about our services and support contact us on sales@superiorltd.com
or call +44 (0)1202 854300.

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If you would like to learn more about how Superior can contribute to your business’ success, we would be pleased to welcome you to meet our people, see our facilities and discuss your needs.
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