Maschinelle Sortierung von frisch eingeschnittenem Schnittholz

850 pieces of structural timber (European spruce, Picea abies) with cross-sections 50 to 95 mm thick and 85 to 295 mm wide were machine graded at three different stages of production, using a bending/radiation type grading machine: Immediately after sawing (green, sawn surface), after kiln-drying to approx. 12% (dry, sawn surface) and after planing (dry, planed). They were then subjected to strength and stiffness tests in bending and tension according to EN 408. Machine grading of green sawn timber resulted in correlation coefficients between 0.73 and 0.80 and approximately the same yield as compared with machine grading off dried and planed timber. In all cases yield was higher than that obtained with conventional visual grading according to DIN 4074.