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  • 1.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Flodin, Jens
    Choosing green sawing dimensions for best value yield of Norway spruce: industrial measurements and physical modelling2010In: Proceedings, 11th International IUFRO Wood Drying Conference: [... in Skellefteå, Sweden, January 18 - 22, 2010 ... the theme of the conference was "Recent Advances in the Field of Wood Drying"] / [ed] Tom Morén; Lena Antti; Margot Sehlstedt-Persson, Luleå: Luleå tekniska universitet, 2010, p. 168-174Conference paper (Refereed)
  • 2.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Flodin, Jens
    Drying shrinkage of sawn timber of Norway spruce (Picea abies): industrial measurements and finite element simulations2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 1-2, p. 41-48Article in journal (Refereed)
    Abstract [en]

    Industrial measurements of green and dry cross-section dimensions were performed for 189 Norway spruce (Picea abies) centre-yield boards with dry dimensions 51 times 149 mm. Two, three or four boards were sawn from each log, depending on log size. Different approaches were used for simulations of cross-section shrinkage during drying. An analytical model, an elastic, an elastic- mechanosorptive and an elastic- plastic finite element simulation model were tested. Thickness and width shrinkage and deformation were simulated. Shrinkage results were compared with each other and with the experimental results. All simulation models gave roughly the same degree of agreement with experimental results except for the centre board from the three-board sawing pattern. For the other boards, the analytical model was not generally better or worse than the results from the finite element models. Shrinkage deformations in finite element models that included mechanosorption or plasticity were nearly the same as for the elastic finite element model except for the centre board of the three-board sawing pattern. The mechanosorptive model was the best model for the shrinkage of the centre board of this sawing pattern except for mid-thickness shrinkage. Comparison between the different finite element simulation models of stresses in the centre board revealed large differences.

  • 3.
    Flodin, Jens
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    On fingerprint traceability in the forestry supply chain2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tracing material through the forestry supply chain is a relatively untapped source for process and product improvements. Since the supply chain handles large quantities at high speeds, have a diverging flow and several different sub processes and people involved along the way, traceability rapidly becomes very complex. The papers presented in this thesis have been focused on tracing wood material by means of the fingerprint approach. The fingerprint approach rests on the foundation that each piece of wood is a unique individual with unique features and that it would be possible to identify and connect individual pieces in the supply chain in the same way that human beings can be identified by the use of their fingerprints. The results from paper I show the importance of preserving the shape of the log and handling the bark assessment at an individual level when trying to connect logs between the log sorting station and saw intake using their 3D outer shape. Paper II and paper III show very encouraging results in connecting sawn timber to the log they were sawn from by using 3D and x-ray data for the logs and surface scanning for the sawn timber. The results show that over 95 % of the sawn timber could be connected to the correct log.

  • 4. Flodin, Jens
    et al.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fingerprint traceability of logs using the outer shape and the tracheid effect2008In: Forest products journal, ISSN 0015-7473, Vol. 58, no 4, p. 21-27Article in journal (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that, among other benefits, could be used to more effectively control and pinpoint errors in the production process. The fingerprint approach is a traceability concept that in earlier studies has shown good potential for tracing logs between the log sorting station and the saw intake. In these studies, bark has been identified as a large source of measurement inaccuracy. This study was set out to investigate whether the fingerprint recognition rate could be improved when compensating for bark with traditional bark functions or a new automatic bark assessment based on the tracheid effect. The results show that the fingerprint recognition rate can be improved by using more sophisticated bark compensation. Compared to no bark compensation, improvements can be made by using the existing bark functions, and even further improvements can be made by using automatic bark assessment based on the tracheid effect. The results further show that the butt-end reducer between the log sorting station and the saw intake has a very negative effect on the fingerprint recognition rate, but that significant improvements in the recognition rate can be achieved by excluding the section of the log's butt end that is affected by the butt-end reduction.

  • 5. Flodin, Jens
    et al.
    Oja, Johan
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Fingerprint traceability of sawn products using industrial measurement systems for x-ray log scanning and sawn timber surface scanning2008In: Forest products journal, ISSN 0015-7473, Vol. 58, no 11, p. 100-105Article in journal (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that, for example, could be used to more effectively control the production process and the utilization of raw material. The fingerprint approach is a traceability concept that rests on the principle that every piece of wood is a unique individual with unique properties and therefore can be identified and separated if a sufficient number of these properties are measured accurately enough. This study was made with the aim of making the fingerprint connection between logs and the center yield sawn from those logs using length and knot information. The material used was Scots pine logs from six different diameter groups sawn with a two-ex sawing pattern into six different dimensions of center-yield planks. The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner in combination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fed surface scanning system situated in the sawmill's green sorting station. The results show that over 95 percent of all planks could be matched to the right log. This gives a high potential for further development and realization of fingerprint tracing between the log sorting and the green sorting station into a practical application for process control and process improvement.

  • 6. Flodin, Jens
    et al.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Fingerprint traceability of sawn products using x-ray logscanning and sawn timber surface scanning2007In: Quality control for wood and wood products: COST Action E 53 the first conference, October 15th/17th, 2007, Warsaw, Poland / [ed] Marek Grześkiewicz, Warsaw: Warsaw University of Life Sciences , 2007, p. 39-42Conference paper (Refereed)
    Abstract [en]

    Traceability in the sawmilling industry is a concept that could be used to more effectively control the production processand the utilization of the raw material. The fingerprint approach is a traceability concept that rests on the idea that everypiece of wood is a unique individual with unique properties and hence can be identified and separated if a sufficientnumber of these properties are measured accurately enough. This study was hosted by a sawmill in northern Sweden andwas aimed at making the fingerprint connection between logs and the center yield sawn from those logs using length andknot information. The 140 logs involved in the study were of Scots pine with top diameters spanning the range from 153 to213 millimeters. The center yield sawn from these logs was of two dimensions. The smaller logs (153-187 mm) were sawnwith a 2 ex pattern to 50 by 100 mm, and the larger logs (174-213 mm) were sawn to 50 by 125 mm with a 2 ex pattern.The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner incombination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fedsurface scanning system situated in the sawmill's green sorting station. Both systems are used in the sawmill's normalcontinuous production. The results show that over 90% of all planks could be matched to the right log, which bespeaksa great potential for further development and realization of fingerprint tracing as a tool for process control and processimprovement.

  • 7.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Flodin, Jens
    Vikberg, Tommy
    Nyström, Jan
    Lundgren, Nils
    Monitoring lumber size, shape and mismatch in double-arbour saws-Development and validation of scanning equipment2009In: Proceedings of the 19th International Wood Machining Seminar / [ed] Handong Zhou; Nanfeng Zhu; Tao Ding, Nanjing: Nanjing Forestry University , 2009, p. 222-227Conference paper (Refereed)
    Abstract [en]

    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.

  • 8.
    Grönlund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Flodin, Jens
    Wamming, Thomas
    Adaptive control of green target sizes2009In: Proceedings of the 19th International Wood Maching Seminar / [ed] Handon Zhou; Nanfeng Zhu; Tao Ding, Nanjing: Nanjing Forestry University , 2009, p. 87-94Conference paper (Refereed)
    Abstract [en]

    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.

  • 9. Lundgren, Nils
    et al.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Flodin, Jens
    Choosing green sawing dimensions for Norway spruce from stochastic simulations2011In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 57, no 2, p. 94-99Article in journal (Refereed)
    Abstract [en]

    The high accuracy of log positioning and the stability of saw blades in breakdown machinery in modern sawmills have reduced the need to add margins for sawing variations. Oversize green sawing dimensions are still needed, but mainly to allow for drying shrinkage. This has put a new focus on better adapting green sawing dimensions to the shrinkage behavior of wood. In this study, a method for optimization of green sawing dimensions using stochastic simulation is presented. Normal distributions were generated for planed dry dimensions, kerf width, and target moisture content. The minimum share of boards exceeding the specified dry dimensions was decided, and deformations in boards from all positions in the cross section in a number of logs were simulated. The simulated shrinkage allowance from stochastic simulations was compared to experimental results from an industry test and to finite element results based on material data for Norway spruce. The results showed that the green width of the sawn boards should increase when the number of boards in the center yield increases. The green thickness of boards should be thinner for center boards and outer boards than for inner boards

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