Large volumes of small parts: (cost-) efficient coating

Wet-chemical drum coating is a new way of coating that is particularly well suited to large volumes of small parts. It allows these parts to be coated efficiently and cost-effectively. We will introduce you to the technology involved and the possibilities it opens up.

How does wet-chemical drum coating work? In a rotating drum small metal, rubber, wooden or plastic components are evenly sprayed with a paint while the parts move over each other. The parts are heated by infra-red radiation or a stream of hot air. The use of both decorative coatings and functional coatings (friction-reducing coatings on O-rings, anticorrosive coatings and electrically-insulating coatings) is possible.

At the PaintExpo trade fair in Karlsruhe we spoke with two suppliers of drum coaters: Special Coatings and Walther-Trowal.


The SC-Coater® (from Special Coatings GmbH & Co.) was developed in 2005 in Germany at the request of companies that had difficulty coating small parts uniformly. In this high-tech coating machine, components can be effectively and efficiently provided with a coating thanks to the specially developed paint system. All this is done in a way that is economical, environmentally friendly and gives a high-quality result. For example, with the SC-Coater® overspray is limited to about 5 percent, whereas with conventional paint methods it often exceeds 50 percent.  Special Coatings acts as a jobcoater for brands like Bosch, Siemens and the Brandstätter Group (Playmobil), but it can also offer its services as a machine builder.


The Walther-Trowal company offers similar systems in the form of its Rotamat drum coaters. These differ mainly in that hot air rather than infra-red radiation is used to heat the components.

Both the drum speed and angle can be adjusted to allow parts with various geometries to move over one another in a uniform manner so that they are homogeneously coated. Once the spray parameters (volume, spray pattern) and the parameters for the drum have been optimised, the coating process is fully automated, which ensures great reproducibility.