Material charge: The laser distance meter aligns side boards and ensures an optimal occupancy rate © Fabian Pöschel
With an overall sawmill yield of more than 63%, Joakim Limberg – shift supervisor at Fiskarheden – is more than satisfied. In September last year, USNR installed the new edging line. Currently in the initiation phase, Fiskarheden's employees have so far achieved an output rate of up to 65 boards per minute. The system is fully automated and the new edger operates without a direct operating worker.
During Timber Online's visit, Eckart Müller, Account Manager at USNR, explained how such impressive speeds with such a high yield rate are possible.
High level of automation: Thanks to the control station, unmanned edging in the workshop is possible
© Fabian Pöschel
Boards from Dalarna
The enterprise based in Transtrand in central Sweden has 125 employees and produces 340,000 m³/yr of rough sawn goods in different dimensions. With a yield rate of 63%, this makes for a roundwood demand of 550,000 sm³/yr. In extended double-shift operation, the sawmill exclusively processes pine supplied within a purchasing radius of 250 km. 94% of the final product are delivered to international markets. Top buyer countries are Northern Africa, Japan, and Poland. 30 years ago, Olle Larsson took over the enterprise that was originally founded in 1923. This makes the sawmill one of the few privately run ones in Sweden.
The software on which the system is based controls the edging such that the highest yield rate is achieved © Fabian Pöschel
Currently, Fiskarheden is modernizing the factory in Dalarna. In the course of this modernization, Larsson invested in a new edging line. He was looking for a system with high capacity and quality. An existing line from Söderhamn Eriksson was the trigger for examining modern versions of the same product.
Ever since Söderhamn Eriksson's takeover by American enterprise USNR, the technology has been going under a new brand name. The on-site visit revealed: engineers have been skillfully making use of synergies such as the combination of established scanner technology and the mechanization in the more recent past.
It is subtle details that allow for the high speeds: Smooth transportation is essential at high feed rates when hauling boards © Fabian Pöschel
American scanners, Swedish shields
The control stand of the sawmill has a futuristic feel to it. The machine operator uses a large number of screens for handling the new line. Thanks to elaborate details, additional staff is no longer necessary. It is the combination of scanners and mechanics in particular that makes this possible. The laser distance meter determines the line's occupancy rate and automatically controls the board feed to prevent overlap. At high speeds, this requires technical subtleties. One example Müller gives is the continuous chain conveyor that prevents warping at the handover. Furthermore, slight elevations help to smoothly transport unedged lamellas.
USNR focusses on continuous chains and elevations at handover points © Fabian Pöschel
Just in case, side boards can be boxed back and re-fed before the optimization scanner. The centerpiece of the system is not the well-functioning circular sawing unit that takes care of the actual edging, but rather the optical laser scanner that determines the exact trimming spot. Müller elaborates on the advantages during the tour: "The scanning module Bioluma 2900 from USNR stands out since it is a closed system. This prevents malfunctions due to resin formation or contaminations." The computed data are directly interpreted by the company's own software and transmitted to the sawing unit.
Scanning systems: Eckart Müller (left) in front of the optimizing scanner and Joakim Limberg in front of the laser distance meter © Fabian Pöschel
Track-keeping device and centering arms
This kind of high-speed edging that follows right after scanning is mainly possible due to two developments: On the one hand centering arms that vertically align boards by means of plastic lamellas that are arranged on top and keep them in track horizontally by means of laterally positioned rolls. On the other hand, the conveyor chains are equipped with distinct rakes that accelerate the boards.
The splinter cutter is operating at speeds of up to 460 m/min and the edging saw can process boards with lengths of up to 6 m. If the side boards need to be rip sawed, a separating module that can be added downstream of the splinter cutter is used for splitting the boards with up to four saw blades. This is followed by a brake belt that reduces the speed of the boards by means of a pneumatic plastic hatch.
Limberg is motivated after the installation phase: "Provided regular maintenance, the line is functioning really well. Once we have completed the training period, we will be aiming for at least 70 boards per minute."
