Potentially increased sawmill yield from hardwoods using X-ray computed tomography for knot detection

Abstract

& Context One of the most important wood defects affecting the value yield from European beech (Fagus sylvatica [L.]) logs is knots that are visible on the sawn wood surface. The non-invasive technology of X-ray computed tomography (CT) can be used for the assessment of log internal features, especially the geometry and position of knots before primary breakdown to support the decision of value-optimised log rotation in sawmills. & Aims The objective of this study was to test whether valueoptimised log rotation can be performed successfully by using the CT-derived knowledge of internal knottiness for the hardwood species beech. & Methods Size parameters of 670 knots were measured and their position was marked in CT images from 33 logs. The 3Dreconstructed logs were virtually sawn in 12 different rotational angles using the software InnoSIM. This allowed visual grading of the simulated sawn wood and the calculation of product volume and value. & Results The results show that if optimal rotation was applied to each single log, both total volume as well as total product value yield could be improved by up to 24 % compared with the average yield of all simulated rotational angles. & Conclusion In this small-scale study, it is demonstrated that CT technology could be used to support the decision about optimal rotational angle of beech logs to maximise volume and value yield.

Performance of strength grading methods based on fibre orientation and axial resonance frequency applied to Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and European oak (Quercus petraea (Matt.) Liebl./Quercus robur L.)

“…In general, application of machines based on such models have provided the most accurate strength grading that has been available on the market in recent years (Hanhijärvi and Ranta-Maunus 2008;Olsson 2016). As regards the possibility of using X-rays to identify knots on the basis of difference in density between knots and clear wood (Oh et al 2009), it should be noted that such density contrasts are generally larger in softwoods than in hardwoods, which implies that knot detection using X-rays is more useful for softwoods than for hardwoods (Stängle et al 2015;Viguier 2015).…”

Knot detection in computed tomography images of partially dried jack pine (Pinus banksiana) and white spruce (Picea glauca) logs from a Nelder type plantation

“…logs based on 38 CT data can improve value yield by about 13 %. Stängle et al (2015) showed that value and 39 volume yield of beech (Fagus sylvatica L.) logs can be increased by up to 24 % when 40 optimizing log rotation based on CT data, compared to an average value from 12 different 41 rotations.…”

Applications of computed tomography (CT) scanning technology in forest research: a timely update and review

“…Current market prices for sawn wood of each quality grade and the by-products were used to estimate the value increase that would result from the optimized log rotation. Stängle et al (2015) concluded that changing the log rotational angle led to large differences in the volume and value of product yield, as calculated from the sawing simulations, and that potential optimization of volume and value per log was highest for logs of low quality. Based on their results, the authors also indicated that using a CT scanning system to detect log internal defects would allow better performance of hardwood sawmills in the future.…”