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Articles by Mats Warensjö

Category: Research article

article id 388, category Research article
Jacob Edlund, Mats Warensjö. (2005). Repeatability in automatic sorting of curved Norway spruce saw logs. Silva Fennica vol. 39 no. 2 article id 388. https://doi.org/10.14214/sf.388
Sawn wood from curved logs is prone to have cross grain and contain compression wood, both of which affect the dimensional stability. Different types of curvature can, however, have different effects on both the sawing process and board quality, which is why a standard measure of bow height alone is not enough to sort logs or set the log quality. The aim of this study was to evaluate the repeatability when sorting curved saw logs using a 3D log scanner. In the study, 56 logs were categorized into five different curvature types and four different degrees of curvature severity. The logs were run through a Rema 3D log scanner four times, and the external geometry was recorded. From the geometry data, variables describing log shapes were calculated and used to develop models using linear discriminant analysis, which was used to classify the logs according to curvature type. The accuracy and repeatability were evaluated for the classifications with Cohen’s simple Kappa coefficient. The results of this study showed that it is possible to sort logs by curve type using a 3D log scanner, although sorting by curve type was largely dependent on curve severity. The repeatability test determined that the chance of a curved log being graded identically two consecutive times was 0.40, measured as kappa.
  • Edlund, SLU, Department of Forest Products and Markets, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: jacob.edlund@spm.slu.se (email)
  • Warensjö, SLU, Department of Forest Products and Markets, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail:
article id 424, category Research article
Mats Warensjö, Göran Rune. (2004). Stem straightness and compression wood in a 22-year-old stand of container-grown Scots pine trees. Silva Fennica vol. 38 no. 2 article id 424. https://doi.org/10.14214/sf.424
The distribution of compression wood in relation to eccentric growth and development of stem straightness was studied in a 22-year-old Scots pine (Pinus sylvestris L.) stand in central Sweden that was established with container-grown seedlings. Stem straightness was measured on the same 440 trees in 1986 and 1997. The number of stems with straight base sections increased from 60% in 1986 to 89% in 1997. Measurements of 72 sample trees in 2001 showed that 96% of the trees had developed straight stem bases. External geometry data of the logs was obtained with a Rema 3D log scanner. A sub-sample of 16 trees was randomly selected for analysis of compression wood distribution and eccentricity measurements. From each tree, 11 discs were cut at every 60 cm along the stem. All discs, except one, contained compression wood. Compression wood and pith eccentricity was most pronounced near the stem base but not significantly correlated to basal sweep. Severe compression wood content was correlated to pith eccentricity and bow height. In general, correlations were better for the basal sections of the logs. Even though most trees were straight, they contained large amounts of compression wood. It is evident that eccentric growth and compression wood formation play major roles in the development of stem straightness. In several stems, a spiral compression wood distribution pattern was found. Reasons for this are discussed.
  • Warensjö, Department of Forest Products and Markets, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden ORCID ID:E-mail: mats.warensjo@spm.slu.se (email)
  • Rune, Department of Forestry and Wood Technology, Dalarna University, SE-776 98 Garpenberg, Sweden ORCID ID:E-mail:
article id 623, category Research article
Anders Roos, Matti Flinkman, Armas Jäppinen, Mats Warensjö. (2000). Adoption of value-adding processes in Swedish sawmills. Silva Fennica vol. 34 no. 4 article id 623. https://doi.org/10.14214/sf.623
Adding value to lumber by processing it after sawing and standard drying is one means for the sawmilling industry to increase market shares in competition with other materials, e.g. glass, steel, concrete, aluminium, and plastics. In this study the adoption patterns of value-adding processes used in Swedish softwood sawmills were analysed based on production data from 1995. About 90% of the sawmills applied a value-adding process after initial sawing and drying, and 72% of the sawmills applied two or more processes. The total share of processed sawnwood was about 40%. Important dimensions of value-adding processes are: extra drying and production of blanks for doors/windows and for furniture; surface-treatment, mainly planing, which is sometimes associated with preservation and painting; length trimming and pallet production; extra drying and production of edge-glued panels and laminated beams; and stress grading and production of building components. The association of different value-adding dimensions with location, ownership and production characteristics were investigated. The total share of value-added production were higher for private sawmills than for mills owned by forest companies or by forest owners’ associations, and it was higher for mills in southern Sweden than for sawmills in other parts of the country. Value-added share does not clearly correlate with mill size or with the dominating tree species being sawn.
  • Roos, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: anders.roos@sh.slu.se (email)
  • Flinkman, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail:
  • Jäppinen, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail:
  • Warensjö, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail:

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