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Summary of industrial view on strengthgrading based on interviews
RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.ORCID iD: 0000-0002-7945-7518
RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
RISE Research Institutes of Sweden, Built Environment, Building and Real Estate.
Luleå University of Technology, Sweden.
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2020 (English)Report (Other academic)
Abstract [en]

This report presents the industrial view regarding strength grading, based on interviews with personnel of sawmills and manufacturers of grading systems. The sawmills are Swedish, German and Austrian enterprises, while the manufacturers are from Sweden, Finland, Germany and Italy. The interviews were performed during 2019 and 2020.

In the last two decades, knowledge has been accumulated with respect to raw material characterisation of wood, from the standing tree to the end product.

It is known that log pre-grading has the potential to significantly improve raw material utilisation, because at that stage of production one is still free to choose the cutting pattern(sawn product dimensions). 3D-log scanning immediately before sawing allows improving log rotation and positioning for cutting optimisation to maximise volume yield, which is already widely used in sawmills.

One of the major technological breakthroughs of the last years is the development of industrial computed tomography log scanning, which provides a much more detailed insight into each individual log than 3D outer shape log scanning and discrete X-rayscanning.

Three new approaches to strength grading is presented: pure log grading; integrated grading, where log information is used to improve the precision; sequential strengthgrading, where log pre-grading is followed by board grading.

The interviews show that the use of automatic strength grading is different between the countries. In Sweden all mills use some automatic grading system, while German mills rely to a large extend on visual grading.

The answers show that the interviewed industrial persons in general have knowledge about the capabilities of log sorting and grading with 3-D, discrete X-ray and computer tomography, CT. The knowledge about acoustic log scanning is not as good as for the other techniques.

The interviewed sawmillers had in general a strong sense that log tomography could improve the yield, both in volume and value, from the logs. But in contrast to that, the Swedish sawmillers were confident in that CT is a significant improvement over the other scanning techniques. The German sawmillers did not have the same confidence in the CT-scanning´s possibilities. Only few of the Swedish and the German sawmillers saw any large potential in adding acoustic scanning to the other log scanning techniques.

The large Austrian enterprises were mainly interested in the possibilities, the advantagesand disadvantages of the new technology of industrial computed tomographyfor round timber. For the other Austrian companies, the focus was on less cost intensive systems such as scanners for determining the dynamic modulus of elasticity, logouter shape or grain deviations.

The most important features for grading are knots, their position, status and size. Alsorot and top rupture are important to be able to make a good grading of the log. A more“fuzzy” grading is also wanted, meaning that the rules shall not be too strict.

The manufacturers in general said that normal development is ongoing. Larger, revolutionary, inventions will not be presented in this manner.

Place, publisher, year, edition, pages
2020. , p. 24
Series
RISE Rapport ; 2020:93
Keywords [en]
3D-scanning, CT-scanning, logs, strength grading, wood, x-ray
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-51008ISBN: 978-91-89167-78-0 (electronic)OAI: oai:DiVA.org:ri-51008DiVA, id: diva2:1509794
Available from: 2020-12-14 Created: 2020-12-14 Last updated: 2023-05-09Bibliographically approved

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Lycken, Anders

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