Automatic grading of sawlogs: A comparison between X-ray scanning, optical three-dimensional scanning and combinations of both methods

Abstract

As sawmills become increasingly efficient, the importance of focusing on value recovery becomes obvious. To maximize value recovery, sawmills require the ability to sort logs according to quality. This study compares four different combinations of three-dimensional (3D) and X-ray scanning that can be used to grade logs automatically. The study was based on 135 Scots pine (Pinus sylvestris L.) logs that had been scanned with both a 3D scanner and an X-ray scanner with two X-ray sources. The percentage of boards with correct grade sawn from automatically graded logs varied from 57% when using only 3D scanning to 66% when using a combination of 3D scanning and X-ray scanning in two directions. The highest possible result, with ideal log grading, was 81%. The result also shows that the combination of a 3D scanner and one X-ray direction results in higher accuracy than a scanner based on two X-ray directions.

Keywords:

• 3D scanning
• automatic grading
• Pinus sylvestris
• PLS
• sawlogs
• sorting
• X-ray

Acknowledgments

The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning funded this study.

Notes

Oja, J. ^1,2 , Grundberg, S. ^1,2 , Fredriksson, J. ² and Berg, P. ² (¹Luleå University of Technology, Division of Wood Technology, Skellefteå Campus, Skeria 3, SE-931 87 Skellefteå, Sweden, and ²Swedish Institute for Wood Technology Research, Skeria 2, SE-931 77, Skellefteå, Sweden). Automatic grading of sawlogs: a comparison between X-ray scanning, optical three-dimensional scanning and combinations of both methods.

Additional information

Notes on contributors

Johan Oja

Oja, J. 1,2 , Grundberg, S. 1,2 , Fredriksson, J. 2 and Berg, P. 2 (1Luleå University of Technology, Division of Wood Technology, Skellefteå Campus, Skeria 3, SE-931 87 Skellefteå, Sweden, and 2Swedish Institute for Wood Technology Research, Skeria 2, SE-931 77, Skellefteå, Sweden). Automatic grading of sawlogs: a comparison between X-ray scanning, optical three-dimensional scanning and combinations of both methods.