Alles aus einer Hand EN Everything from a single source

Kallfass provided the entire mechanisation for the new cross-laminated timber plant of Stora Enso in Gruvön/SE and was responsible for the entire concept, including safety control…

Kallfass, located in Baiersbronn/Germany, is well known as a mechanisation specialist. The same applies to the fact that the mechanical engineering company equips cross laminated timber systems. With this in mind, we can refer to some well-known projects. Recently Kallfass has added a CLT press (Cross Laminated Timber) and a CLT turning device.

The mechanical engineering company Kallfass from the Black Forest has already been involved as a supplier in several cross laminated timber projects in Austria and Germany. The most recent work completed was that of Stora Enso in Gruvön/Sweden. Construction work on this site began in 2018 and the system has been running in automatic mode since the beginning of 2019.

To date, this is the largest project for Kallfass in the area of cross laminated timber applications. The company not only supplied the entire mechanical equipment—from the feeding of packages to the acceptance of the finished pressed elements—but was also responsible for the overall layout and the complete safety control system. The fact that Stora Enso has selected Kallfass as its supplier is probably also due to the fact that Kallfass has already been involved in the Austrian CLT plants in Ybbs and Bad St. Leonhard, Austria. The total capacity in Sweden totals 100,000 m3/year.

Large packages also possible

Stora Enso also operates a sawmill in Gruvön, Sweden which supplies the raw materials for the laminated timber elements. The sawn timber (dried and battened or pre-planed) is transported by truck to the Kallfass feeding station. This feeding station is also designed for large packages up to 5.8 m long, 2 m wide, and 3 m high. A vacuum-operated de-stacking device separates the packets layer-by-layer. If stacking strips are available, a brush automatically scrapes them off and collects them. The Kallfass mechanism separates the layers and feeds the boards piece by piece to Finscan's quality scanner. In this area, the strength and the moisture of the timber is also measured. Any unsuitable workpieces are ejected from the process.

Two paths for the boards

“The scanner provides us with the information whether there are cracks on the front sides or knots in the base of the finger joints. If this is the case, we trim the front sides," says Kallfass Managing Director Hans Haist. The boards pass through a front end cross-cut with adjustable servo stop. Subsequently, the zero line is changed and the same process takes place on the other side of the board. If the scanner also finds undesirable wood features in the centre of the board, these pieces are ejected to an upper level where a cross-cut system made by PAUL Maschinenfabrik GmbH cuts out these areas. “However, this concerns only about 5% of the total quantity. Most of it goes straight on to the Grecon finger-jointing system”, describes Kallfass Project Manager Helge Widmann.

The Kallfass mechanisation cycles both the long workpieces and the cross-cut lengths from 800 mm upwards at a rate of up to 50 boards per minute. They travel in the direction of the finger-jointing system with the continuous press. Subsequently, the mechanisation takes over the finger-jointed lamellas again downstream of the moving cross-cut saw. These lamellas are between 8 and 16 m long. The applied adhesive can now cure on a 25 m long buffer section before Kallfass feeds the lamellas into the Rex planing machine. After the lamellas are pre-planed, they are cycled in the direction of the board press: First, a system provided by OEST Mineralölwerk GmbH, applies a layer of adhesive to the the lamellas. Subsequently, these lamellas are fed into the glueing press made by DIMTER GmbH. The single-layer boards produced in this way are then taken over again by a Kallfass system.

This is where the paths split: A VOITH crane picks up the longitudinal layers and transfers them to the intermediate storage. Previously, a chop saw, installed downstream of the glueing press, has already cut the longitudinal layers to the width required by the order. In order to make the best possible use of the DIMTER press, the longitudinal layers are always produced in 16 m lengths wherever possible. If shorter boards are required, Kallfass has developed a special system to recycle the remnants of the longitudinal layer.

Transverse layers measuring up to 1.5 m are stacked by Kallfass to a height of 2 m and are also transported by a VOITH crane to a second storage area. These processes are fully automated. A controller determines the suitable storage location.

Vereinzelung der Pakete

Sawed with millimetre precision

Now, the longitudinal and transverse layers are combined to form a layer package. The longitudinal layer already has the right format. The transverse layers, measuring up to a maximum of 1.5 m long, come from five buffer locations and are transferred to a 16 m long conveyor. Several boards are placed one after the other on this conveyor until the required board length is reached. If the length is exceeded, a saw cuts the transverse layer accordingly. The timber offcut then becomes the beginning of the next layer. Subsequently, vacuum systems alternately lift the single-layer boards onto a conveyor belt upstream of the press until the layer package is completely assembled. “Several CTL boards can also be laid on top of each other using a dry joint”, explains Widmann.

Downstream of the MINDA CLT press, Kallfass again takes over the multiple press layer package, separates the elements by means of a push-off process, and transports the elements to the grinding machine. Downstream, they are supplied to a VOITH crane, temporarily stored or transported to one of the three Hundegger machining centres.

In the interview Widmann mentions two more figures regarding the safety concept: “At the Stora Enso factory in Gruvön, 1.2 km of fencing and 82 safety doors were installed”.

Full-service provider

However, Kallfass cannot “only” supply the mechanisation for a cross laminated timber factory. Since last year the company also has a CLT press in its product range. “We have developed this CLT press in response to numerous customer requests”, explains Haist. Thanks to it modular and stand-alone segmental design, it makes no difference whether the layer package is built up of boards or pre-glued panels. The customer also has flexibility when it comes to the design of the workpiece. The board dimensions range from 7 to 20 m long, 2.2 to 3.6 m wide, and 6 to 60 cm high. The hydraulic system forms the core of the system. It enables an almost isobaric (without pressure difference) pressing process. In addition to vertical pressure, Kallfass also equips the cycle press with cross pressure units on request. The area-dependent pressure control enables a pressure in excess of 1 N/mm2 even at maximum plate width.

Kallfass will complete its CLT product range with a further innovation in the future: “We have developed a board turning device for cross laminated timber, which can turn the elements very easily and quickly”, explains Widmann. The turning device handles CLT up to 16 m long, 3.6 m wide and 300 mm thick. It is designed for a weight of more than 10 t. “With this device, CLT can be turned over without any risks and without hurting anyone. For example, in joinery centres, one area of application is for two-sided processing", concludes Haist.

Kallfass presented its new CLT press for the first time last year at the LIGNA Expo in Hanover, Germany.

Vereinzelung der Pakete

Kallfass supplied Stora Enso with the entire mechanisation in the cross laminated timber system – the picture shows the separation of the packages in layers.

The scanner (A) detects cracks and knots, the Kallfass saws (B) cut off the front sides accordingly.

Modular design: Kallfass manufactures the CLT press in segments so that it can be adapted exactly to customer requirements

Mechanisation of the longitudinal (left) and cross layers (right) before they are assembled into the layer package.

Turn once, please: To bring the longitudinal layers to the correct side, Kallfass installed a board turning device.

Text Martina Nöstler, Pictures Kallfass, Holzkurier BSP-Special 2020