Automatic coating of windows and doors with a spraying robot

A window manufacturer switched from manual painting to automated robot painting. The entire three-coat process for windows, front doors and façade elements is now carried out fully automatically by a spraying robot.

The southern German family business Krazer Fensterbau has implemented a pioneering project together with the Austrian paint manufacturer Adler: In the newly set up surface area, windows, front doors and façade elements are coated with a spraying robot from the primer to the top coat - fully automatically and to the highest quality.

Krazer Fensterbau is a company like many others in Germany: A small, fine craftsman's firm, with tradition, character and the quality awareness of a master craftsman's business. By specializing in high-quality windows, doors and glass façades, the family business from Mutlangen (Baden-Württemberg) has gained an excellent reputation and implements sophisticated projects ranging from upmarket residential buildings to listed buildings. For some years now, senior boss Siegfried Krazer has been supported by the next generation with daughter Jasmin, a newly qualified master glazier, and son Michael, who completed his Master's degree in Rosenheim. Generational changes are often an opportunity to bring a breath of fresh air into the company, rethink established processes and try something new. In the case of Krazer Fensterbau, however, it wasn't just a breath of fresh air - rather, Michael Krazer ignited a veritable whirlwind and implemented a project that had never been seen before in this form in Germany.

It had been planned for some time to relocate production from the existing, cramped company building in the center of Mutlangen to a hall in the industrial park. The production processes were also put to the test, especially those in the surface area. Until now, Krazer had been coating in the same way as many smaller window manufacturers: the windows were dipped by hand and then intermediate and top-coated on the manual spraying stand - a time-consuming process in which each window had to be handled several times and was also error-prone and material-intensive. There should be a better way, thought Michael Krazer - and Hans-Jürgen Benzinger, his customer advisor at Austrian paint manufacturer Adler, had the right answer. The new coating process developed by Adler allows the entire three-layer structure to be applied fully automatically using a spraying robot.

At the heart of the innovative system is the Aquawood Primo RSQ spray primer. "Wooden windows are usually primed by dipping or flooding and then intermediate and top coats are applied by spraying. For manufacturers, this usually means either investing in a complete industrial coating system or coating by hand in the traditional way," explains Matthias Stötzel, Head of Window Application Technology at Adler. "With our new spray primer, the entire coating process can be carried out using a spraying robot. This enables a high degree of automation with a calculable investment and space requirement." The advantages: Short throughput times, minimal material and cleaning requirements, enormous savings in working time, a clean working environment. And above all: a significantly higher surface quality, because the even application with the robot means that runs, cloud formation, fingerprints and dust marks are a thing of the past.

With Michael Krazer, Benzinger and Stötzel were knocking on open doors. "On the one hand, manual painting with exhaust air was out of the question due to the energy concept of our new hall and the heating with a heat pump. On the other hand, we were also looking for ways to make the work easier through automation," says Krazer. Together with Matthias Stötzel, he worked out a process in which the primer, intermediate coat and top coat are sprayed with the robot in recirculating air mode. From planning the new system and fine-tuning the painting process and material to programming the robot, commitment and teamwork were required until even the most complex window elements were perfectly coated in the most delicate shades. "Our application technology team and Thomas Tuschy as field technician did a great job," praises Matthias Stötzel. "After all, our new coating concept not only involves high product quality, but also a great deal of research work and process knowledge relating to system and processing technology."

The effort was more than worth it: "Of course, it took a lot of work to get everything up and running, but thanks to the excellent support from Adler, everything is now running like clockwork," explains Michael Krazer. The new system masters the entire production spectrum: wood and wood-aluminum windows, front doors and façade elements, opaque and glazed, on any type of wood and in any color. The elements are initially suspended in one of the 20 crossbeams, run through the spraying robot three times, and drying and intermediate sanding are carried out on the suspended part. This is just one of the many advantages that Krazer lists: "We used to have to fill 60 liters of material into the dip tank alone - now we work with 4-liter cans, can plan our requirements well and always have fresh material. A color change is done in a few minutes, cleaning effort, material loss and rinsing water quantities are minimal.

Even large-format and heavy parts can be coated without any problems, the workshop is clean and we have hardly any heat loss thanks to the recirculating air operation of the spraying robot." In addition, the surface quality has increased significantly and is consistent without the need for reworking - and makes everyday work much easier: "The robot is easy to operate and works completely independently. Coating happens more or less on the side and we have more time for other tasks." Switching the coating process to the innovative Adler system proved to be a real stroke of luck, according to Michael Krazer: "We now have all the advantages of a high degree of automation, adapted to the general conditions of a traditional craft business. This is an excellent investment in the successful future of our company!" (OM-5/26)