Soft cloud for noble matte shine

A renowned household appliance manufacturer invested in a new powder coating system with dense phase powder conveying. In addition to a significant improvement in quality, an increase in flexibility and cost-effectiveness was achieved.

At its plant in Lehrte, Germany, the household appliance manufacturer Miele develops and produces appliances for commercial laundry care, as well as trough ironers, household ironing systems, air purifiers and components for other Miele locations. In addition to stainless steel fronts, customers want appliances with powder-coated surfaces. A special feature of the Professional sector is the comparatively low volume of custom-made products and the high variance in components, which have widely differing geometries.

For Miele, the wide variety of product shapes and the desire for greater flexibility when changing colors were important reasons for switching from a single-color to a multi-color booth. Andreas Eichbaum, technical project manager at the Lehrte plant, explains: "In the laundry care sector, a lot of work is done with alkalis and bleaches, which can also come into contact with the paint. We therefore have to be able to prove the corresponding resistance and also guarantee it to the customer. At the same time, we have a clear visual premium requirement, which means coatings should look good and must be professionally finished." Eichbaum adds: "We want to ensure that components are coated consistently well and precisely over time. That also means with narrow spreads, i.e. how much powder is applied at each of the different positions."

Before deciding on a new system, Miele thoroughly explored the market and compared various suppliers. "In the end, two criteria were decisive. Of course, Miele stands for quality, or rather the quality of the powder coating. This came first, followed by the price, which was comparable for all suppliers," reports Rainer Freier, who is responsible for purchasing in this area at Miele. The quality of the surfaces to be coated, the mechanical and chemical resistance, but also how the design is reflected were particularly important to Freier when procuring the new system.

Dense phase technology meets current design trends

In recent years, commercial surface design has changed from a glossy coarse texture to a finer texture with a matte gloss level. Such coatings place different demands on process and process control. "That's where we see the very clear advantage in Nordson's new dense phase coating technology over Venturi pump technology," Eichbaum says. "This also coincides with the recommendations from our powder supplier that went into our decision."

Also crucial to the purchase decision were the results of tests at Nordson's laboratory in Erkrath, Germany. "Our products, which we produce at the Lehrte plant, have a very high variance. We went to the lab with reference components that reflect our broad spectrum. We then compared the results and found that Nordson delivered the best results for us. On the one hand, this concerned the coating thickness, which was the most uniform, and on the other hand, the component geometries, which are difficult to coat," reports Johannes Reimer, production manager at Miele & Cie. KG in Lehrte.

The Nordson powder coating system consists of the standard ColorMax3 quick color change booth, Spectrum HD powder center and PowderPilot HD control system, eight Encore HD automatic guns, and final filter and double cyclone. The system was installed at Miele in March 2021. "We had a very ambitious schedule for the entire project," says Andreas Eichbaum, "partly because we wanted to replace the system during ongoing operation." During the two shifts during the day, production in Lehrte could continue undisturbed, and the third shift was then used for the rebuild. The coordination with Nordson went very well both in advance and during the two-week set-up phase. In the third week, the first programs were tested, the plant was run in, and trial operation was able to start relatively quickly. "We had a very clear schedule and after a total of six weeks we went into series operation as planned," reports Eichbaum, who is very satisfied with the project support provided by Nordson. "The way the system was assembled, delivered and commissioned also fully met our requirements."

Economical coating of component clusters

The new coating system is used to coat hundreds of different but recurring components. Corresponding coating programs have been set up for the surface treatment of the component clusters, which always achieve the same results with repeat accuracy. Maximum process control is made possible by dense phase conveying of the powder, so that programs only have to be created once for the various components.

Likewise, coating very deep components has become much easier due to the soft powder cloud of the HDLV dense phase technology. Products are not only coated frontally, but top and side surfaces are also coated. "The door on our washing machines is a very present component, also for the end customer. This component was traditionally coated by hand. With the new system, we have succeeded in completely automating this manual coating," reports Eichbaum. Thanks to the soft powder cloud, both sides of the component can now be coated with the appropriate uniform coating thickness. The scattering could be significantly reduced compared to before, which results in a considerable powder saving.

Nordson Germany GmbH www.nordson.com