The Value of Wood

Production Strategies in the Forestry-Wood Chain Using X-ray Scanning and Computer Simulation

In this thesis, the hypothesis was that the complexity of the forestry- wood chain can be handled by scanning technique, mainly using X-ray, and computer simulation of the operations in the forestry-wood chain. The main aim has been to show how value can be gained by the use of these methods. 

The forestry-wood chain is the process of turning a tree from the forest into a wood product. In this chain, many actors are involved in making decisions, and processing a material that is complex. This means that the decisions are often sub-optimized, since it is difficult to assess the effect of each individual decision on the whole chain and therefore the final product.

An integration of the forestry-wood chain would mean that properties of trees are linked to those of wood products. If this was achieved, better decisions for the entire chain could be made. One suitable tool to augment this integration is computer simulation, since it allows experimentation with different decisions in complex systems, in a short time frame.

Furthermore, the development of industrial X-ray scanners, in par- ticular computed tomography (CT) scanners, enable a higher degree of control of the sawing process, and makes it possible to steer the flow of raw material at an early stage of the forestry-wood chain.

The following results were obtained as part of the overall aim of this thesis:

A method for reconstructing knots in logs enables the creation of log models for sawing simulation from industrial X-ray scanning data. It can be used for studying a larger log material, but for individual logs the errors when predicting sawn timber quality are rather large.

Sawing simulation of 269 CT scanned Scots pine and Norway spruce logs showed that it was possible to achieve a value gain of the sawn timber of up to 21 % when the log sawing position was optimized based on CT data. Such an optimization meant rotating curved logs away from the horns down position, which can have a detrimental effect on the warp of the sawn timber. Logs with a bow height of more than 15 mm should be sawn in a position close to horns down to avoid this, while straighter logs can be freely rotated. This was showed in a test carried out at a sawmill.

An integrated approach means decision making regarding the entire forestry-wood chain at an early stage, which requires a large computational capacity and a large amount of data to process. The data amount can be reduced by a developed method where knots in logs are projected onto a plane to make decisions regarding the rotational position of logs. This decision method improved value and quality of the sawn timber, but was very sensitive to errors in positioning and knot detection.

A simulation tool for cross cutting and finger-jointing, together with CT scanning, showed similar cutting decision results as an industrial sys- tem. The tool was also used to show that a flexible safety distance to knots when cross cutting can increase recovery, compared to using a fixed safety distance, by 3.2 %.

These results show some of the potential of X-ray scanning and com- puter simulation as process control tools, and that developing these further can improve the efficiency of the forestry-wood chain. 

  • Magnus Fredriksson
  • Wood Technology Department of Engineering Sciences and Mathematics, Luleå University of Technology
  • Originalspråk: En

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