With the increasing importance of technical cleanliness, efforts are growing to prevent particle contamination in components or assemblies. Manufacturers must also adapt to updated guidelines in terms of technical cleanliness. OVE Plasmatec, a service provider in the field of elastomer surface finishing, is facing up to these challenges.
The growing demand for technical cleanliness is presenting many manufacturers and suppliers faced with ever greater challenges. Mandatory technical cleanliness is not only required in more and more areas and industries but also places increasing demands on the quality of the parts supplied. Moreover, it is not only about actual cleanliness but also compliance with standards as well as documentation and proof that these processes have been carried out and adhered to. This affects the production of components and component assemblies, as well as logistics, packaging and transportation to the customer’s production and assembly areas.
Regulations on technical cleanliness
Starting in the automotive industry in the 1990s, the demand for technical cleanliness of the parts that were to be installed resulted in stringent requirements, standards and documentation requirements. The VDA, Volume 19 “Testing of technical cleanliness – particle contamination, functionally relevant automotive parts” (2004), define extraction and analysis procedures and the documentation of the test results. This also became internationally valid with the ISO 16232. With the increasing spread of high-performance electronic components and assemblies in automobiles from the 2000s onwards, the topic was the field of electrical engineering and was laid down in the guideline “Technical Cleanliness in Electrical Engineering”.
The production of cleanliness-sensitive parts, assemblies and systems in terms of technical cleanliness is so-called clean production. Along the value chain from raw material through to end use production, assembly, personnel, cleaning, packaging, storage and transportation must be taken into account.
Increasing challenges
With the use of such electronic assemblies in battery-powered or rechargeable systems, the topic is returning to the mobile electromobility to the mobile industry with car and bicycle engines. Likewise, the areas of power tools and household
appliances are increasingly using rechargeable batteries as an energy source. In this context, the High Voltage Directive for power electronics from 2014 is becoming increasingly important. It defines particle limits with regard to electrical clearances, air gap and creepage distance, process reliability and repeatability in series production and the handling of non-metallic particles and fibres.
For manufacture, refinement and use of elastomer seals, this means an increasing effort in the production of clean and functional parts. This is particularly true when the assemblies become smaller and more powerful, and more functionalities are installed within an assembly. As a result, increasingly smaller seals also require special treatment before they start their long-lasting service life. When the volume of a gasket becomes smaller, the ratio of production-related residual particles to the entire component becomes less favourable. It is more important to remove these particles before the seals are finished. Accordingly high is the requirement for technical cleanliness. OVE Plasmatec, a service provider in the field of surface finishing of elastomers, is facing up these challenges – for example on a seal for e-bike electric motors with the size of a pea.
In the plasma process the pre-cleaned elastomers are placed in a low-pressure plasma system. The plasma changes the surface properties of the sealing rings by stimulating the molecules.
The plasma process not only removes any remaining superficial manufacturing production aids but also diffused unbound compound components such as plasticizers from elastomers.
Proof of LABS conformity
The coating of elastomer seals is intended to turn simple sealing rings into high-performance high-tech parts. This allows improvement of their friction coefficients as well as their dynamic functions. An easier assembly for automated processing is often possible by separation and optional colouring of the seals. At the same time, the time-consuming, manual application of conventional production and assembly aids are no longer necessary. The coating with a water-based coating is wafer-thin and highly elastic. The most important prerequisites for its application are absolute cleanliness and certified LABS conformity.
Paint wetting impairment substances (LABS) prevent uniform wetting of the surfaces to be painted and thus cause funnel-shaped imperfections and craters in the paint layer. Since the introduction of low-solvent paints in the automotive industry, LABS conformity has been required for production materials, equipment and tools. Also in the pre-treatment of bonding surfaces, LABS interfering points are not desirable as they reduce adhesion. Materials, components and assemblies are tested for LABS conformity, as it is not known which substances lead to these interferences.
From simple washing to deep-acting plasma cleaning, there is a tested LABS conformity according to various factory standards. While metals and many plastics can be safely removed by intensive cleaning the surface of production aids, with elastomers, surface cleaning is not sufficient. Only the plasma process creates LABS conformity.
Deep-acting plasma process
In the plasma process, the pre-cleaned elastomers enter a low-pressure plasma system, in which a vacuum is first generated. A high-frequency generator supplies electrical voltage which, together with ambient air or oxygen is introduced. This creates an electrically conductive gas, the plasma, which changes the surface properties of the sealing rings by stimulating the molecules.
During this ultra-fine cleaning oxygen radicals (O) and ozone (O3) are created. The free radicals with diffusing non-elastomeric substances combine with residues of the production auxiliaries and oxidise as gas (CO2) and H2O. In this way, not only remaining surface production aids are removed, but also – depending on the material composition – diffused, unbound compound components such as plasticizers from elastomers.
Request for certified technical cleanliness
The requirements resulting from the regulations and standards are also demanded by customers. Since the issue of shortage of skilled workers has come into focus, OVE Plasmatec has noticed an increased demand for documented and certified technical cleanliness. Their conclusion: customers demand precisely the services that are specified in the regulations and standards – i.e. products, components and parts that have the appropriate degree of level of cleanliness and ensure that no undesirable particles, impurities and residues are on the surfaces that could impair quality, functionality and service life. This results in individual requirements based on VDA Volume 19, such as for example the CCC code. The family-owned company also sees small and medium-sized enterprises (SMEs) no reason to shy away from the increasing requirements, guidelines and regulations on technical cleanliness. They are convinced that it is possible to remove particle contamination from surfaces of components or in assemblies, and to maintain guidelines for the manufacture of cleanliness-sensitive parts, without that this exceeds the financial possibilities of SMEs.
Dust filters on windows and air purifiers ensure ultra-clean production conditions.
Bettina Kremer
CEO, OVE Plasmatec GmbH