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- Ekevad, Mats, et al.
(författare)
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Different methods for monitoring of flatness and tensioning in circular saw blades
- 2009
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Ingår i: Proceedings of the 19th International Wood Machining Seminar. - Nanjing : Nanjing Forestry University. - 9787502362249 ; , s. 78-86
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Konferensbidrag (refereegranskat)abstract
- The performance of a circular-saw blade during sawing depends greatly on the mechanical and geometrical properties of the individual saw blade in question. In order to characterize an individual saw blade when manufacturing saw blades or when doing maintenance of the saw blades, flatness and tensioning are important aspects. Flatness and tensioning influence the lateral stability of the saw blade during sawing and thus affect the sawing result, e.g., the accuracy of the dimensions of the sawn timber. Tests and comparisons of different methods for characterizing individual saw blades were done. New and used saw blades with different amounts of tensioning and flatness were used. The tested saw blades had several radial slots and were intended for use in double-arbour saws with collars and no guides. The compared methods were static and dynamic flatness measurements, natural-frequency measurements and theoretical finite-element calculations with different excitation methods and boundary conditions.The results show some of the qualities of the different methods. The benefits and disadvantages are provided, as well. Especially tensioning can be accurately measured and predicted from natural frequency measurements and finite-element calculations
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| 3. |
- Grönlund, Anders, et al.
(författare)
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Adaptive control of green target sizes
- 2009
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Ingår i: Proceedings of the 19th International Wood Maching Seminar. - Nanjing : Nanjing Forestry University. - 9787502362249 ; , s. 87-94
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Konferensbidrag (refereegranskat)abstract
- In Swedish sawmills, about 70% of the total costs can be derived from raw-material costs. Hence, it is very important for sawmills to obtain the highest possible yield. The green target size is an important parameter that affects the yield. The nominal size, sawing allowance, shrinkage allowance and planer allowance add up to the green target size that is needed when sawing lumber. We have, in this work, studied whether it is possible to adaptively control the green target size by measuring log density and annual ring width with an X-ray Log Scanner online. Our hypothesis was that density and growth speed will affect how much every single piece of lumber will shrink.The results show that both density and annual ring width are rather weak variables for prediction of lumber shrinkage. The variable "distance to pith", i.e., where in the log cross-section a piece of lumber has been cut, has proved to be a significant variable for prediction of lumber shrinkage. The results show that the yield can be considerably improved by adapting the green target size to how far from the pith every piece of lumber is cut.
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| 4. |
- Grönlund, Anders, et al.
(författare)
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Monitoring lumber size, shape and mismatch in double-arbour saws-Development and validation of scanning equipment
- 2009
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Ingår i: Proceedings of the 19th International Wood Machining Seminar. - Nanjing : Nanjing Forestry University. - 9787502362249 ; , s. 222-227
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Konferensbidrag (refereegranskat)abstract
- The costs for raw material amount to about 70% of the total costs for most sawmills. Consequently, it is very important to improve the saw yield for the economy and competitiveness of sawmills. The aim of an ongoing project in Sweden is to build knowledge and develop methods and techniques that enable an increase of the sawing yield. The idea is that the yield increase will be achieved through thinner kerfs, adapted shrinkage allowance and lower sawing allowance. One key parameter in the sawing process is sawing accuracy. We have as a part of the ongoing project developed scanning equipment with which we can measure the size and geometry of the produced lumber. The equipment is an off line research apparatus based on two laser triangulation devices.The industrial partners on the project have especially pointed out that a method is needed for measurement and evaluation of the mismatch on sawn surfaces produced by double arbour saw machines. The equipment has a measurement resolution that is better than 0.1 mm in the thickness direction and can measure thickness and width with a repeatability of 0.1 mm and bow, crook, twist and cup with a repeatability of < 1 mm. As there is no standard for measurement and evaluation of mismatch, a special algorithm for this parameter has been developed and correlated against subjective judgements of skilled personnel from the sawmill industry. The correlation between manually judged mismatch and mismatch measured by the scanner was 0.76.
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