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Rolling can give wood products a harder surface
Rolling wood – is it possible? Yes, indeed, it is. A recently concluded project has demonstrated that rolling is a process that can be used to give pine a surface hardness comparable to that of oak.
Swerim has initiated and run a cross-disciplinary project to determine if it is possible to upgrade wood products with the help of technologies which are currently used in the steel industry. In Sweden, production of processed wood products is currently relatively limited, due to competition from low-wage countries, and an automated process for upgrading could enable conditions for competitive and profitable production.
In the project, Swerim, Luleå University of Technology (Wood Science and Engineering) and Sveaskog have worked together to find methods and automated processes for upgrading wood. To test the ideas, pilot trials for rolling wood in Swerim’s own section-rolling mill have been conducted.
The aim of the trials has been to harden pine-board top surfaces (material for flooring). Trials have shown that it is an advantage if rolling is done step-wise, instead of by means of pressing, whereby pressure is distributed over a greater area. Under step-wise reduction, knots in the wood could be reduced to the same degree as the surrounding material, which is a great advantage. Otherwise, knots are known to give rise to irregularities and cracks during processing, something which did not occur in the trials. After rolling, the surface hardness of the wood was equivalent to that of oak flooring.
“Through successful collaboration, we have surpassed the objectives of the project by practically demonstrating that rolling is a useful process for hardening pine,” says project manager Annika Nilsson. “It has been both fun and enriching to work in a cross-disciplinary way between different sectors.”
The rolling force applied in wood rolling is very low in relation to the force applied when rolling steel, which means modest investment costs for those who wish to implement this technique. However, in order to meet customer requirements for dimensional stability, for example, the process will need further development.
The project has been funded via Vinnova’s BioInnovation programme.