Increasing the value of strength graded timber by industrial computer tomography

Computed tomography (CT) scanning has the potential to improve monetary outcome of logs and meets the increasing demands of wood industry for detailed information on timber quality prior to processing. A sample of 38 Douglas-fir logs passed the industrial CT-scanner CT Log of Microtec. Before sawing, a template was sprayed on both end-grains of the logs to enable to create virtual boards corresponding to the real boards sawn. In a validation part, it was investigated the match between virtual and real data using the knot cluster value DAB (DIN 4074).The three largest knot values (DABs) of the virtual boards showed good correlations to the manual boards. In a further optimization part, we wanted to point out the increase of boards’ value by varying the rotation angle; the knot size error – as outcome of the validation – and a rotational error were considered in order to reproduce the real situation. The simulation revealed an average increase of value from 5 % to 20 % compared to the median of all tested positioning combinations depending on the chosen price differences between the strength grades. Sawmill owners can save money since logs can be processed in a better way to final products with increased added value.