Technical coatings optimise the surface of AM parts

Additive manufacturing in combination with existing (coating) technologies provides better and more feasible applications than AM alone. This is the conclusion reached by Sirris and the Fraunhofer-Institut für Angewandte Polymerforschung (IAP) during a joint research project on technical coatings for additive manufacturing. The results are promising.

Additive manufacturing is today making the switch to industrial production. The technology is important for the future and will have an impact on the production market and far beyond. The industry can benefit from the technology with its ability to produce on demand, flexible adaptability and the ability to produce small quantities. However, the surface of produced components tends to be very rough and porous, a challenge tackled by Sirris and the Fraunhofer IAP within a CORNET project TCAM.

Stricter requirements on surfaces

Fraunhofer IAP has built up expertise in technical coatings and Sirris can also draw on the experience that was very useful while investigating the use of technical coatings for AM. The requirements for AM-produced components are expanding and it is essential to ensure consistent material quality for industrial manufacturers. In addition, the requirements in relation to surface quality are also becoming stricter. Thanks to the use of technical coatings, Sirris and Fraunhofer researchers succeed in significantly improving the roughness and porosity of the surface of AM-produced parts. Technical coatings enable a smooth, sealed surface with specific functions.

Surface functionalisation

The research showed that the combination of lacquering and polishing is the most efficient technique for surface optimisation in additive manufacturing. In addition, components can be further functionalised by using special coatings or surface treatments. In the project, the researchers metallised the smoothed components. The metal coating is a visible example of the functionalisation process: improved scratch resistance, antimicrobial and many other properties.

Sirris produced several components manufactured with SLS, SLA and FDM (i.e. 3D printing), with all methods presenting different surface treatment challenges. Each piece was analysed to determine its specific properties, after which the surface was activated, coated, polished and metallised using the most appropriate method. Manual polishing of 3D printed components takes a long time and automation of the polishing process risks changing the shape, especially when it comes to fine details. Fraunhofer IAP assisted in the development of options to overcome the existing problems, especially with regard to porous and rough surfaces.

Combination of production methods

Traditional production methods often reach their limits with complex components. The more complex a component, the more difficult and complicated it becomes for traditional production methods. Additive manufacturing opens up possibilities to make this kind of components faster and more cost efficient. Pieces usually consisting of several parts and have to be assembled afterwards can now be created in one step, while each part of the surface has the required quality. In case of complex parts, some surfaces are also difficult to reach. With suitable surface treatment technologies that may even be integrated into AM machines in the future, it will be possible to fully functionalise even complex parts.

3D printing of steel

Sirris is also involved in a second project on AM - 'INSIDE Metal AM' - together with CRM and BIL, on surface post-treatment. The project focuses specifically on 3D printing of high strength and stainless steel. Based on existing knowledge and additional applied research, the project partners will define guidelines and flowcharts that help to make the choice between production by means of AM or traditional techniques, based on both technical and economic arguments.  In addition, guidelines will be developed that should allow to channel the technical complexity of the AM production process and to deliver a high quality and certifiable product ('first time right') from the first batch. The right surface treatment is also a crucial step. The knowledge and experience collected during the TCAM project will also be used for this purpose.

Read more about the TCAM project here.