First successful CLT press delivered to the Czech Republic
Up to 120,000 m³ of cross-laminated timber will be produced yearly in future in the new Stora Enso plant. With a wealth of expertise and experience gained in three successful CLT projects, the Finnish/Swedish company is, in its collaboration with Kallfass, now placing its faith in a completely new player in press manufacturing. The success achieved indicates just how right those responsible have been.
Successful project management: Kallfass Managing Director Hans Haist with Stora Enso Project Manager Markus Weiss-Moser and Kallfass Project Manager Helge Widmann (r. to l.) in front of the first Kallfass CLT press.
Ever since the initial CLT location in the Carinthian town of Bad St. Leonhard, Kallfass has been responsible for overall mechanisation at Stora Enso. Ždírec in the Czech Republic will now see the opening of the fourth and, henceforth, largest Stora Enso CLT plant. “We're delighted to have found a partner like Kallfass who we known and value since our CLT production was first launched. The overall mechanisation and press concept it has presented has completely convinced us”, says Markus Weiss-Moser, the Project Manager at Stora Enso. Kallfass Managing Director Hans Haist agrees. “We're very proud to unveil our first complete CLT reference project in Ždírec. The plant is among the foremost locations on a global level”.
Fully integrated location
“One enormous advantage of this project is the fact that it's not a completely new greenfield construction in the classical sense, as we can rely on structures that have developed over decades at this location”, says Markus Weiss-Moser. Following its purchase by Stora Enso in 1999, the sawmill has been continually expanded. Sawing capacity (around 550,000 m³ per annum) was expanded two years after the takeover through the addition of solid structural timber production (150,000 m³ per annum). Pellet production also commenced in 2015, with around 80,000 tonnes being produced each year since then.
The addition of cross-laminated timber rounds of the comprehensive package of services the plant provides. The production capacity of the Finnish/Swedish group will, in total, exceed 400,000 m³ per annum as a result.
The zero-joint principle
Cross-laminated timber is manufactured according to the same principle in all four Stora Enso CLT plants. Both longitudinal and transverse layers are produced as single-layer solid wood boards before being joined to create CLT panels. Process reliability is paramount. “Industrial production of more than 100,000 m³ per annum needs to be a very tight operation. Using single-layer boards means we work without loose lamellas. Naturally enough, this high level of quality is also reflected in the approval values the boards must meet”, explains Markus Weiss-Moser.
Trimming the transverse layers: Transverse layers produced as single-layer boards are trimmed to the later board width upstream of the lay-up station.
In Ždírec, practically everything between the outlet of the throughfeed press for single-layer board production to subsequent joining is from Kallfass. “Minimising of interfaces was one of our central goals in the new plant. Having Kallfass as our main machine supplier enabled us to achieve this”, explains Markus Weiss-Moser.
Boards intended for the transverse layer are automatically cut to the desired length and placed in an appropriate intermediate buffer. Creation of the board can commence as soon as all layers are prepared, and the Oest gluing carriage starts to apply glue on the stationary lay-up table. “A special feature deserving mention here is our exclusive use of PU glue in the entire board. This includes the join, edge and surface of the board”, explains Markus Weiss-Moser.
80 press cylinders spread over ten press modules ensure particularly even pressure distribution.
Press number one
The finished layer package is then conveyed into the Kallfass press on a modular belt conveyor. “The conveyor unit is reversible. The great advantage of this is that, should a problem arise during gluing, the incomplete layer package can be moved quickly and easily into the press”, says Hans Haist. “This emergency press operation also enables us to prevent the loss of valuable raw material in rare cases where incidents arise”, adds Markus Weiss-Moser.
The maximum thickness of the layer package is 600 mm. The dimensions of the completed board are between 8 and 16 m in length and 2 to 3.6 m in width. “We're working with four cylinders per press line. This means we can ensure that the pressure required is applied to every square millimetre of the board”, explains Hans Haist. The plant can achieve pressures of up to 1 N/mm2. “Naturally enough, considerably less pressure is required where spruce is the raw material. But we see this as an investment in the future. Who knows which wood types may be interesting in future for cross-laminated timber? This solution means we can react flexibly, regardless of what happens”, says Markus Weiss-Moser.
Following pressing, the individual boards are automatically pushed off at the dry joint and separated again before being transferred to the sanding machine and subsequently trimmed in a total of three portal processing machines from Hundegger.
Series production begins in 2023
The first board was successfully produced in August, and the final authorisation and approval phase is currently under way. “However, everything should be completed as planned by the end of the year, then we can begin single-shift production. We will gradually increase this to four-shift operation by 2026. We'll need around 110 new employees for this at the location”, explains Markus Weiss-Moser.