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Increase of material yield in plywood production with new veneer processing technologies

: Plinke, B.; Aderhold, J.; Berthold, D.

Barbu, M.C.:
Processing technologies for the forest and biobased product industries : PTF BPI 2010; Salzburg University of Applied Sciences, Kuchl/Austria, 7. - 8. Oct 2010
Münster: LIT Verlag, 2010
ISBN: 978-3-643-50219-3
International Conference on Processing Technologies for the Forest and Biobased Products Industries (PTF BPI) <1, 2010, Kuchl>
Conference Paper
Fraunhofer WKI ()

Although Germany has a share of 15 % of all plywood consumed in Europe, the German plywood producers have a market share as low as 1% in Europe. On the other hand, German forests have a high stock of logs suitable for the production of plywood. In order to make plywood production in Germany attractive for investors again, improvements in manufacturing technology are necessary, and new technology should enable plywood producers to broaden their raw material basis [1].
Material yield using present technology is estimated to approximately 40 % due to losses caused by defects, peeling, drying, trimming etc. During the drying process and due to anisotropic shrinking of the veneer ribbon splits and wavy edges appear. Although several methods are used to achieve an "ironing effect", drying losses cannot be avoided. A possible solution could be processing veneer sheets in a hot press. An increase in yield seems possible if the peeled veneers are processed in a way which adapts to the real size and frequency of defects: Clipping of fixed sizes and post-grading is one possibility, and cutting of defects and joining the sheets to an endless ribbon free of defects is the other choice. But a decision one of the alternatives is only possible of the defects on a veneer ribbon typical for the available material are recorded and processing regimes are simulated and evaluated by yield. WKI has developed software for this simulation and tested it for different qualities of beech and spruce logs.