Making the industrial coating of CLT even more ecological

“This investment will further strengthen Stora Enso’s position as a leading global supplier of engineered wood products for low-carbon, sustainable buildings,” Arne Folger, product manager at Sylva Services, explains and adds: “The line is one step in the further development of our Sylva construction kit, which consists of prefabricated wood-based elements for low-carbon buildings. The custom-made elements for every application and requirement – from Sylva walls, ceilings and roofs to stairs, beams and supports – are designed to make the planning and construction of wooden buildings even easier for planners and architects in particular.”

In an interview with the Holzkurier, Christopher Hutter, Senior Project Manager at Sylva Building Solutions, emphasizes: “With the start of trial production and the gradual transition of our facility to production in the fourth quarter of 2023, labor-intensive work along the value chain will be moved from the construction site to the factory. This will result in a substantial improvement of construction quality. The automated coating solution for Sylva CLT walls and floors reduces construction times and results in optimized wood protection. Our customers can choose surfaces in standard colors and benefit from a better protection of their Sylva CLT products from moisture, sunlight and insects.”

Thanks to the smooth collaboration between the in-house and external project teams, the project was practically completed after just one and a half years. During this time, a modern hall with an area of 2,400 m² was built using 800 m³ of Sylva CLT products among other things. In addition to the coating line, new parking spaces for semi-trailer trucks were also built to increase the loading capacity in Ybbs and offer customers higher flexibility in delivery.

Stora Enso, the world’s largest manufacturer of CLT, uses environmentally friendly, water-based coatings. “With the new line, we can apply high-quality water-based coatings on around 500,000 m² of Sylva CLT walls and floors each year, making us the world leader in this segment,” Folger tells us. All of Stora Enso’s products can be surface-treated. The maximum dimensions are 16 by 3.45 m, with a minimum length of 2 m.

Robots do what used to be manual work

The wood preservatives are applied by two CNC robots, each of which is equipped with four high-pressure atomizing nozzles. A portal scanner automatically recognizes the geometry of the elements, and the coating is done according to the customer’s wishes. “All preparations for system components, such as windows and doors, are also recognized and selectively left out. The elements are moved in a vertical position, thereby making it possible to treat only the end grain or two or four sides,” Hutter explains.

Compared to manual coating, this automated line offers a fully controlled process, which also includes a drying tunnel in which warm air flows around the elements. “If necessary, we can also sand elements in between and smooth raised wood fibers,” Hutter adds.

Sustainability across the board

Folger lists the advantages of the preservatives used: “Our coatings offer standard water-based varnishes, protection from UV light, water-repellent impregnation and, optionally, insect repellents. Demand for insecticides could increase in the future, as related legal requirements are now emerging in the Benelux countries following France’s example. From an ecological point of view, water-based solutions are better than conventional, oil-based foils and membranes.”

With four production sites and a production capacity of almost 400,000 m³ a year, Stora Enso is the world’s largest supplier of CLT. Ybbs is the first site with a fully automated coating line. “Other production sites might follow this example. For the time being, though, we could take on and process orders for our other sites,” Hutter says, looking to the future.

“Feedback from partners like ZMP and their customers from the carpentry sector has been very positive. They can save a lot of work and costs on the construction site. Furthermore, an automated line is better able to achieve a uniform and appealing surface,” Folger adds.

Problems solved

CLT projects are getting larger in scale and construction elements have to be stored for longer periods of time. “Just two weeks of exposure to UV light can change the appearance of the wood – and UV light is omnipresent. Our coatings help protect the elements in the early stages of construction,” Folger emphasizes.

The complete line was developed and delivered by Finiture (see page 66), in collaboration with Handl Maschinen from Wels. Assembly only took about five months, from April until commissioning in the third quarter of 2023. The line has seven color wheels, two of which are permanently loaded for quick color changes. By using containers with capacities of up to 1,000 l, the line has sufficient capacity available.

It is not only the Ybbs production site that profits from this coating line. Stora Enso’s customers, in particular, benefit from it, as they receive high-quality timber elements which are even more sustainable.