Automatic sorting of sawn birch [Elektronisk resurs] Defect detection possibilities on sawn and planed wood surfaces

• In the production of sawn hardwood a critical processing step is the quality grading. The grading has normally been handled manually in the hardwood sawmills. The process has been labour intensive and a problematic working environment. With the help from existing scanning technology it is possible to automate the process with several benefits as a result. These are e.g. a decreased need of labour, a better working environment and the possibility to use more complicated grading rules. Thereby the wood could be used in a more optimal way with both cost and environmental benefits. One problem when grading hardwood is that camera and laser based scanning technology has mainly been used on planed surfaces. Normally the quality grading in hardwood sawmills is performed before planing. The wood may then be cross-cutted to components before planing in order to minimise the volume losses because of deformations of the wood pieces. In order to investigate the possibilities to scan the sawn wood before planing rip-sawn birch boards ( Betula pubescens Ehrh., Betula pendula Roth.) was scanned before and after planing the wood. The used scanner was a commercial system for automatic sorting of wood. Before the scanning it was estimated that the sawn surfaces exposed to the surrounding environment during drying would not generate any usable results from the scanning. Therefore only the two rip-sawn surfaces were used for evaluation before and after planing. The evaluation was made by comparing the results from the quality grading before and after the planing based on grading rules used by Swedish hardwood sawmill. The results show that there are possibilities to grade the birch wood before planing. The study, however, shows that the scanner has difficulties in detecting small colour variations as brown streaks and fresh knots. It is also difficult to detect fibre angle deviations because of loose fibres on the sawn surface. The possibilities to scan the birch wood are thereby related to the grading rules, i.e. if the mentioned quality parameters are allowed or not. 

Ämnesord

Agricultural Sciences  (hsv)

Agricultural Science, Forestry and Fisheries  (hsv)

Wood Science  (hsv)

Lantbruksvetenskaper  (hsv)

Lantbruksvetenskap, skogsbruk och fiske  (hsv)

Trävetenskap  (hsv)

Forestry and Wood Technology  (lnu)

Skog och träteknik  (lnu)

Genre

government publication  (marcgt)

Indexterm och SAB-rubrik

Automatic sorting

Scanning technology

Birch

Sawmilling