WEIG KM 3: Reliable coating quality with OptiCoat Layer curtain coating station

WEIG’s KM 3 operator Andreas Eifler and Valmet’s Project Manager Martin Taxacher examine the new OptiCoat Layer curtain coating station.

Due to the challenging market situation in recent years, WEIG Group’s board machine KM 3 has had to adapt to the market’s increasing quality demands. They decided to invest in new coating technology for two main reasons: to improve the board’s surface appearance, and to reduce the mill’s carbon footprint by aiming for better energy and material efficiency.

The previous coating method could not keep up with the speed and production increases that had gradually taken place over the years. “We wanted to eliminate the streaks the old air knife left in the coating, which led to a significant amount of broke, and we wanted to reduce our ecological footprint by saving drying energy. Web breaks were also an issue in KM 3 before the rebuild,” explains Wolfgang Zawadzki, Head of Project Department & Mechanical Planning, Deputy of Board Plant at WEIG.

Our quality-sensitive customers have particularly noticed the improved appearance and have also praised it.

The mill produces white lined chipboard with a basis weight range of 250–550 grams per square meter. For this particular board grade the surface properties are very important. “It has very good processability in subsequent processes such as printing and gluing, and of course, a very good appearance. Because of this, the surface of the board is particularly important, especially the even distribution of the coating color,” explains Dr. Boris Rotter, Head of Technology at WEIG. The new curtain coater has already improved the surface appearance of the board. “Our quality-sensitive customers have particularly noticed the improved appearance and have also praised it,” he adds.

Reliable and uniform coating

A state-of-the-art OptiCoat Layer curtain coating station replaced the old air knife coater. The new technology was the right decision and has been working smoothly. “The curtain coater itself is very easy to operate, simple in construction, and very stable in operation, and it has not caused us any problems in the first few months that we have been operating it,” says Michael Fuhrmann, Head of KM 3 Operations at WEIG.

The new curtain coater has significantly improved coating coverage.

The new curtain coater has solved the quality issues that were the main reason for the investment. “Before, the application pattern of the coating color was very streaky, which we have now improved with the curtain coater. Now we have very homogeneous and even coating color application. We can also better control the application amount of the coating,” says Fuhrmann.

Web breaks have not been an issue since the curtain coater installation, which has had a positive impact on machine efficiency. Coating color losses are also smaller than they used to be. “The losses for the new coating color preparation are generally lower because we have fewer streaks and defects, fewer washing cycles, and fewer losses during cleaning,” explains Fuhrmann. According to Zawadzki, the coater’s maintenance has been efficient: “The operators particularly appreciate the significantly lower maintenance effort, and I receive consistently positive feedback from the team,” he says.

Securing the investment with pilot trials

After the investment decision, the choice of technology was confirmed with pilot trials at the Valmet Paper Technology Center in Järvenpää. The trials were conducted with raw base board rolls that were first manufactured at WEIG’s own production facilities and then shipped to Finland for the trial runs. The pilot trials were successful confirming that the chosen coating technology was the right one. “We were very impressed by the high technical level of the pilot facility and the high competence and professional working methods of the Valmet’s team,” says Rotter. 

We were very impressed by the high technical level of the pilot facility and the high competence and professional working methods of the Valmet’s team.

The results achieved in the pilot trials have been reached also in production: “The pilot trials already demonstrated the significant quality improvement that we later saw in production after installation,” says Rotter.  “Of course, we are still optimizing the coating color formulation, but we must say that the operation is very stable and reliable,” adds Fuhrmann.

OptiCoat Layer curtain coating station at Weig’s board machine KM 3.

Great cooperation as the basis for a successful project

The collaboration between Valmet and Weig has been great from the very beginning of the project: The sales phase was smooth; the delivery of all the components was efficient; and the installation was successful due to great pre-planning. “We were very impressed by the prompt style Valmet operated already before the order was placed. This was also because we had a contact person with whom the chemistry was absolutely right,” says Zawadzki. One of the project’s main challenges was its very tight schedule, but with great cooperation the machine started up on time. “We only needed 24 hours to ensure a marketable product,” stresses Zawadzki.

Great cooperation between Weig and Valmet ensured the project’s success.

Overall, this project has been a model of effective cooperation between a technology supplier and papermaker. “It was a very pleasing project with a high technical level, professional teams, and it was characterized by partnership-based collaboration,” says Rotter. “We would gladly undertake projects of this style with Valmet at any time. Weig considers this project very successful from all perspectives,” adds Zawadzki.

Text: Veera Silakoski

Photos: Paavo Pengermä, North Arrow Films