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- Axelsson, Ann, et al.
(författare)
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Potential for increasing volume yield by reducing planing allowance
- 2017
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 12:5, s. 301-306
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Tidskriftsartikel (refereegranskat)abstract
- About half the volume of sawlogs ends up as sawn and planed timber. The rest is lost due to drying shrinkage or is turned into by products. As the raw material is a major expense for a sawmill, it is important to reduce waste.To investigate how much the volume yield in the production of sawn and planed timber could be increased by reducing the target dimensions in the sawing stage in a sawmill, two groups of sawn timber were planed under similar conditions. One group consisted of sawn Scots pine timber with a large variation in twist. The other group consisted of sawn Norway spruce timber planed under different pressure settings. Using X-ray images, the minimum dimension for avoiding planer misses was calculated for each board, to find the smallest green target dimension. This was compared to actual measured dimensions.It was found that most sawn timber had unnecessarily large dimensions, and it was also found that a reduction in the target dimensions could increase the volume yield for sawn and planed timber by more than 3 percentage points. Boards with large twist would however need a higher planing allowance. The effect of the planer pressure setting was negligible.
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| 2. |
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| 3. |
- Cool, Julie, et al.
(författare)
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Knot detection in coarse resolution CT images of logs
- 2017
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Ingår i: International Wood Machining Seminar (IWMS-23).
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Konferensbidrag (refereegranskat)abstract
- The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.
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| 4. |
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| 5. |
- Fredriksson, Magnus, 1984-, et al.
(författare)
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A sawmill simulation study of the volume yield changes when sawing with thinner kerfs
- 2020
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Ingår i: Proceedings of the 2020 Society of Wood Science and Technology International Convention. ; , s. 363-376
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Konferensbidrag (refereegranskat)abstract
- Using thinner sawblades in sawmills has a potential for both increasing volume yield and decreasing energy usage in the sawing process; possible secondary effects of this are reduced outtake from forests or at least a better use of what is harvested, lower greenhouse gas emissions and higher productivity. How much the sawing kerf can be reduced depends on several factors, such as maintaining the stability of the sawblade, feeding accuracy and so on. This study deals with the possible volume yield increases when reducing the sawing kerf, based on different possible scenarios of which some are more realistic to achieve in the near future than others. The study is based on simulated sawing of 1464 Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) logs. Tests were made for both circular sawblades as well as for band saws, deployed in a cant sawing process with a primary and a secondary saw. Both variable sawing patterns as well as fixed sawing patterns was investigated. In the first case, the choice of sawing pattern was optimized based on volume yield, while in the latter case, logs were presorted on top diameter into log classes that were each assigned a specific sawing pattern. The results show an increased yield of about 1.3 to 1.5 percent units per mm reduced sawblade thickness, and a maximum theoretical yield of 57-59 % for a 0 mm saw kerf. The latter is of course not possible to achieve in practice, but it hints at the maximum potential of reducing the sawblade thickness. In the near future, it is expected that a kerf reduction of around 1 mm is possible. This would thus result in a possible yield increase of 1.3-1.5 percent units, with further increases depending on improvements in sawblade design, sawblade stabilization, improved materials, and machines that are more accurate. Possible future studies include quantification of secondary effects from the yield increase; effects that can help mitigate deforestation and climate change, with a retained level of production volumes.
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| 6. |
- Fredriksson, Magnus, 1984-, et al.
(författare)
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Automatic Knot Detection in Coarse-Resolution Cone-Beam Computed Tomography Images of Softwood Logs
- 2019
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Ingår i: Forest Products Journal. - : Forest Products Society. - 0015-7473. ; 69:3, s. 185-187
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Tidskriftsartikel (refereegranskat)abstract
- X-ray computed tomography (CT) scanning of sawmill logs is associated with costly and complex machines. An alternative scanning solution was developed, but its data have not been evaluated regarding detection of internal features. In this exploratory study, a knot detection algorithm was applied to images of four logs to evaluate its performance in terms of knot position and size. The results were a detection rate of 67 percent, accurate position, and inaccurate size. Although the sample size was small, it was concluded that automatic knot detection in coarse resolution CT images of softwoods is feasible, albeit for knots of sufficient size.
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| 7. |
- Fredriksson, Magnus, 1984-, et al.
(författare)
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Factors Affecting Volume Yield in a Forestry-Wood Value Chain : A Simulation Study Based on CT Scanning
- 2017
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Ingår i: Pro Ligno. - Romania : Pro Ligno Foundation. - 1841-4737 .- 2069-7430. ; 13:4, s. 540-548
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the results of a simulation study, where log models based on CT scanned logs of Scots pine (Pinus sylvestris L.) was used as input material to a computer simulation model of a generic value chain involving sawing, drying, crosscutting and finger jointing. The aim was to investigate which factors that affect the volume yield in the value chain, be it forestal, log-, process- or quality-related factors. The results show that factors related to growth conditions and log size have a large impact on the volume yield in the studied value chain, together with quality requirements on knots. Factors such as sawing positioning and log quality had a much smaller impact. It can be concluded that it is possible to model a forestry-wood value chain, while assessing which input variables affect the result in terms of volume yield, using CT scanning of logs and subsequent computer simulation of the production processes.
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| 8. |
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| 9. |
- Fredriksson, Magnus, 1984-, et al.
(författare)
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Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs
- 2017
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Ingår i: International Wood Machining Seminar (IWMS-23).
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Konferensbidrag (refereegranskat)abstract
- X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored in the log yard they dry to a certain extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. The objective of this research was to investigate the effect of drying on knot detection in Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual measurements for this purpose, and the results show that knot detection was clearly affected by partial drying. Because dried heartwood and sapwood have similar densities, the algorithm had difficulties detecting the heartwood-sapwood border. Based on how well the heartwood-sapwood border was detected, it was statistically possible to sort logs into two groups: 1) Low knot detection rate, and 2) High knot detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. Therefore, logs that are partially dried out and fall in the low knot detection rate should be handled cautiously because the optimization results based on CT knot detection cannot be fully trusted. Sawing of these logs could be optimized using only their outer shape, ignoring internal quality. Similarly, only logs having a regular heartwood shape should be used when scanning logs for research purposes or in databases of CT scanned logs. Finally, a larger knot detection rate was obtained for Jack pine. This could have been facilitated by the fact that pine trees usually have larger but less numerous knots than spruce trees.
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| 10. |
- Fredriksson, Magnus, 1984-, et al.
(författare)
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Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from a Nelder type plantation
- 2017
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Ingår i: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 47:7, s. 910-915
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Tidskriftsartikel (refereegranskat)abstract
- X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored they dry to some extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. This paper investigates the effect of improper heartwood-sapwood border detection, possibly due to partial drying, on knot detection in jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual reference knot measurements, and the results showed that knot detection was affected by detected heartwood shape. It was also shown that logs can be sorted into two groups based on how well the heartwood-sapwood border is detected, to separate logs with a high knot detection rate from those with a low detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. This can potentially aid both sawmills and researchers working with log models based on CT.
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