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Dynamic seals prevent fluids from leaking or mixing between two machine components that are moving in different directions. Surface textures, such as dimples, can improve seals’ performance by reducing the friction they produce. However, current methods of adding texture involve finishing each seal after it is moulded. That makes it expensive for manufacturers – in Europe, mostly SMEs – to make surface-textured dynamic seals.
So researchers from the TDM-SEALS project developed technology to add surface texture during the moulding of the seals, saving production time and costs. Central to the technology is a non-stick coating on the moulds, which helps release the seals quickly and cleanly from the patterned side that creates the surface texture. And to help manufacturing SMEs adapt this technology to their customers’ requirements, the project has developed tools and a methodology for designing the most appropriate texture for specific uses of dynamic seals.
Four European national plastic and rubber component trade associations are behind the initiative for the EU-funded project, says project coordinator José Ramón Valdés of Spain’s Instituto Tecnológico de Aragón. They wanted to collaborate with researchers and specialist SMEs to develop high-value niche products that could make the industry more competitive.
Seal customers – typically hydraulic and pneumatic equipment and automotive manufacturers – could also benefit. Tests in TDM-SEALS on prototype textured seals showed they cut friction by over 20 % compared to smooth seals. This makes the seals last longer and reduces the energy consumption of machines that include them.
Technical advances
To limit the sticking that can damage seals as they are manufactured, while simultaneously cutting mould cleaning costs, project researchers trialled anti-stick coatings on moulds in which textured seals are made. This improved demoulding by over 30 %. The project tested coatings made of ceramics and sol-gel coatings – tiny molecules of solids dispersed in a liquid to form a solid – which are well-known technologies and should be easy for manufacturers to add to moulds, says Valdés.
The project’s research also increases knowledge on friction. Although there is already a lot of evidence that texturing reduces friction on hard, rigid surfaces such as ball bearings and metals, says Valdés, TDM-SEALs provided some of the first scientific evidence that texturing soft elastomeric (stretchy) components reduces friction. And because it is not common in the rubber industry to measure the force needed to extract a moulded object from a mould, the researchers developed a test rig that mimics rubber demoulding and that can be used for more research.
SME opportunities
Test data, prototype seals, the test rig and the texture design method are all available to project SMEs and SME associations to help them promote and adopt the project’s technology, says Valdés. The research team also plans to provide technical help with designing texture patterns for specific industrial applications.
Valdés says that the project’s techniques could create skilled jobs in texture pattern design, and create business opportunities for mould makers, laser texturing companies and coating companies.
The financial rewards for seal manufacturers alone could be high. A study from the project estimates that companies producing 5-20 different models of seals from coated texturing moulds could make annual profits of € 100 000-120 000 per seal type, depending on the complexity of the seal and on other technological and business factors.
The associations in the project consortium were very happy with the results, adds Valdés. They are now encouraging their members to use the TDM-SEALS technologies. At the same time, consortium members are investigating opportunities to take the TDM-SEALS research further or develop new technologies for seals and plastic components – either together or with similar partners.