Please activate JavaScript!
Please install Adobe Flash Player, click here for download

uni'wissen 02-2013_ENG

saw this species of conifer as the ideal object of research for their project due to its straight growth and the fact that it covers 60 percent of the demand for timber in Germany. A regional sawmill cut the spruce logs into floorboards, which the researchers then sorted into 15 groups on the basis of their surface characteristics. Some of the boards were flawless, some of them had small, dark knots, others light, large knots, and still others had striking growth ring patterns. On the basis of this characterization, members of Becker’s team at the Institute of Forest Utiliza- tion fashioned two-meter square floor patterns in their woodworking shop, which they then used as material for their survey of test subjects at trade fairs and on the internet. Becker and Man- uel found it interesting which floor was the most and which the least well liked. “In order to con- vert these subjective opinions into objectively measurable parameters, we took the idea from the Swedish study of using pairs of terms to de- scribe the optical qualities of the wood: calming – disquieting, symmetrical – asymmetrical, life- less – lively, and so on,” says Manuel. “We then asked the test subjects which words they associ- ated with the floor patterns.” The forest scientists found out that, for example, some customers prefer floor patterns with a lot of small knots, be- cause they find them lively, while others find the same patterns to be disquieting. At this point in the project, the scientists from the FVA come into the picture in order to ensure that the logs can be sawed to create the wood surface the customers want. They take x-rays of the logs by means of computed tomography (CT) to capture inner characteristics of the wood, such as the form, size, and location of the knots. This involves sliding an x-ray source equipped with detectors along the entire longitudinal axis of the log over the course of approximately 20 minutes. The result is a three-dimensional CT image of the inner structure of the log. The re- searchers can then use this model to create a computer simulation that indicates the precise way in which the log needs to be cut to achieve an end product with a lot of small knots or only a few large knots. This makes it possible to create timber with a surface that meets customer pref- erences. Only Attractive Products The CT scanner the team used for the project is now being developed into an industrial scan- ner that will only need a maximum of 20 seconds to x-ray the logs. This would allow sawmills to improve the cutting area on their own. In the long term, the researchers hope that this technology will lead to a situation in which only attractive products reach the market and poorly selling product lines can be avoided. The final results of the project are not yet certain. The scientists are currently analyzing the survey to determine which surfaces customers like best. It has al- ready become clear that the wood does not have to be flawless to be appealing: “A small but sig- nificant percentage of the customers prefer The two- and three-dimensional illustrations show where in the log the knots are located (marked red and yellow). The researchers use this information to determine how floorboards (illustration on left, light blue lines) need to be cut to meet customer preferences. Illustrations: FVA Baden-Württemberg 34