Successful powder coating of non-metallic workpieces

In order to be able to powder coat non-metallic workpieces as well, a contract coater was looking for a suitable system. With an electrostatic powder coating system, the company can now successfully powder coat materials such as plastics and wood.

Brandt has been active in professional industrial painting for 50 years and is today one of the leading contract coaters in Denmark. The company employs around 100 people at its headquarters in Varde, Denmark. In order to be able to respond to a wide range of customer requirements, Brandt covers the entire technology spectrum - from manual coating to highly automated painting systems in the wet paint and powder areas. Customers include manufacturers from the wood and furniture, metal, construction and plastics industries.

Brandt already has many years of experience in wet painting and powder coating of metal components. However, the demand for coating sensitive substrates is steadily increasing. These include organic and mineral materials (such as wood-based materials or plastics), fiber cement panels and a variety of hybrid material composites. They are processed, for example, into MDF kitchen fronts or window frames. Many of these materials have no or very low electrical conductivity and are sometimes very temperature-sensitive.

Government environmental regulations and VOC guidelines in wet painting are becoming increasingly restrictive. Brandt was therefore looking for a sustainable powder coating solution that could also be applied to sensitive substrates - materials that are traditionally often wet painted. In addition to the smaller environmental footprint, another advantage of powder coating is the significant savings in resources. The surfaces are coated seamlessly, are scratch-resistant and extremely durable.

After a careful analysis with corresponding application trials, experienced specialists from Wagner (Ursin Huwiler, Mats Rapp, Niels Ole Larsen, Janus Wemmelund), TRIAB (a Scandinavian system house supplier of powder ovens) and selected powder coating manufacturers developed a flexible system concept, which was installed at Brandt at the end of 2021.

With the electrostatic M-Line powder coating system, Brandt, as one of the first companies in the Scandinavian region, can also offer powder coating for non-metallic substrates. Non-conductive, temperature-sensitive materials such as plastics and even inhomogeneous natural materials such as wood are powder coated with high efficiency in a material-friendly manner. To achieve this, the coating system can process highly reactive low-temperature powders and UV powders in addition to conventional metal powders.

The M-Line system comprises ideally matched components, which ensure that different powder coatings can be applied with a high application efficiency, even on non-conductive materials. A core element here are the suction pipes arranged on both sides along the coating booth, which minimize the air flow in the coating zone. The field controllers used improve the grounding of non-conductive or only slightly conductive workpieces, optimize the coating thickness distribution and prevent the so-called picture frame effect. The special geometry of the piping and the monocyclone reduces the pressure loss in the system and the risk for powder deposits. This so-called Energy Efficiency Package (EEP) from Wagner reduces the friction of the powder during recovery, which generates less heat energy. This enables gentle recirculation of the highly reactive low-temperature powder. To control the complete plant technology, including automatic guns and motion units, Brandt uses the SuperCenter EVO powder center with Twin Sonic Sieve. Powder conveying and color change processes are thus automated and very reliably executed.

Preheating and melting processes take place in infrared (IR) ovens. Curing is then carried out using either electrical infrared (IR) or ultraviolet (UV) technology in the TRIAB "Speedoven UV". A precise interplay of infrared radiation, convection air and ultraviolet radiation makes it possible to completely cure extremely temperature-sensitive substrates already at below 120°C and within 2-3 minutes.

Brandt can achieve savings in many areas: With the Energy Efficiency Package, the coating system requires up to 40 percent less energy than comparable systems, as a smaller fan motor is sufficient to generate the same extraction volume in the coating booth. Brandt has been able to significantly improve its environmental balance sheet with the new powder system. In addition, in contrast to wet painting, no solvents are produced. Thanks to the recycling of overspray powder, an enormous amount of material is saved. With the robust 1-layer powder technology, which does not require any intermediate sanding, Brandt also significantly reduces manual processes. Compared to wet painting, the throughput time per workpiece can be significantly reduced: About one minute of preheating, about one minute of powder coating, about five minutes of curing in the oven and about 20 minutes of cooling - in total, the throughput time for a circulating layer is only about 30 minutes.

For Brandt, the system opens up completely new possibilities: Thanks to the highly flexible overall concept, the contract coater can now successfully process a wide range of non-metallic objects and materials and can respond more flexibly to customer requirements. (OM-2/23)