– It is gratifying that the equipment is in place, especially when the need now has become so large. The goal is to make Luleå University of Technology in Skellefteå one of the world leaders in research on wood welding and surface modification of wood through friction. We want to be an attractive partner in international research projects, but also a natural partner for the Swedish timber industry at a future industrial implementation of the technology, says Dick Sandberg, Chair Professor in Wood Science and Engineering at Luleå University of Technology.
Fast vibrations instead of glue
Wood welding is a way of joining wood without the use of glue or other additives. The process utilizes frictional heat generated by letting the wood surfaces to be joined quickly vibrate against each other under pressure. This result in the deformation of the wood cells and chemical changes occur. Between the wood surfaces a bonding material occurs that functions as glue.
– The technology can also be used to modify a surface of wood (wood fusion), such as hardness or increase its ability to withstand water. Studies show that pine can be processed to be twice as hard, as oak, says Mojgan Vaziri, Associate Senior Lecturer in Wood Science and Engineering at Luleå University of Technology, who got a PhD in wood friction welding in 2011.
It is these areas, wood joinery and wood fusion, which is expected to have great potential for industrial applications.
– Where large amounts of glue are being used, for example in finger jointing, the costs can be significantly reduced by wood welding, moreover, it becomes far more environmentally friendly. Regarding wood fusion, making the surface of soft woods like spruce and pine harder makes it competing with hardwoods such as beech and oak in applications such as flooring and countertops, Mojgan Vaziri says.
Wood Science and Engineering in Skellefteå has a leading position in research on wood welding. Since a number of years the research group have an international cooperation with the University of Bern and the National School of Wood Science and Timber Engineering in France, which gave access to welding equipment for wood.
– Our partners have focused on hardwood, which does not have an industrial significance in Sweden. Therefore, we try to transfer the existing results to our Swedish wood, mostly pine and spruce. We also want to intensify research in surface modification, a largely unexplored area, which requires frequent tests with our new vibration welding machine. This would be economically unfeasible if we had continued to carry out the tests in Switzerland or France, says Mojgan Vaziri.
The vibration welding machine is manufactured by Branson and cost 2.2 MSEK with accessories and is funded by the Kempe Foundation (900'), companies in WoodCentre North (700') and LTU’s lab Fund (600').