Simulated yield in a sawmill using different measurement technologies

Abstract

The potential of using different scanning technologies for measuring the shape of sawlogs is evaluated. The operation of 1-and 2-axis shadow scanners, a 3-d scanner and a 3-sources X-ray scanner is simulated, however, without taking measurement inaccuracy into account. The crosssectional shape at the top end of 100 Scots Pine (Pinus silvestris) logs and 106 Norway spruce (Picea abies) logs was used in the study. These shapes are measured manually and the operation of the different scanners, that is, the measurements and the shape predictions leading to a decision on the sawing pattern, is simulated. Different technological situations as whether the bark has or has not been removed by the time of scanning, and whether the rotation of the logs at sawing is random, fixed or optimized, are considered. The performances of the scanners in the different situations are given in terms of the average main yields. The results show that there is a yield increase of ca. 0.5 percentage points when replacing a 1-axis shadow scanner with a 2-axis shadow scanner. There is a further potential yield increase in introducing a 3-d scanner or an X-ray scanner, however, in order to get a substantial improvement using these scanners one has to control the orientation at sawing. The difference in yield of the 3-d scanner between random and optimized orientation is ca. 2 percentage points when measuring on bark and ca. 4 percentage points when measuring under bark. Abschiitzen der Ausbeute einer Siigerei bei Verwendung unterschiedlichen MeBmethoden fiir RundholzquerschnitteDie Nutzungsm6glichkeit verschiedener Metkechnologien zum Erfassen von Rundholzquerschnitten in einem S~ige-betrieb werden bewertet. Die Verfahren mit ein-und zweiachsigen Scannern, einem 3D-Scanner sowie einem dreiachsigen R6ntgenscanner wurden simuliert, allerdings ohne Beriicksichtigung ihrer Fehlergrenzen. FUr die Untersuchung wurden die oberen Querschnitte yon 100 Kiefernst~immen und 106 Fichtenst/immen verwendet. Deren Querschnittsformen wurden zun/ichst handvermessen, danach die verschiedenen Verfahren simuliert, mit denen die Querschnittsform bzw. dieEinschnittspl/ine berechnet werden. Dabei wurden auch verschiedene Situationen beThis work has been supported by the Norwegian Research Council. riicksichtigt, je nachdem, ob mit oder ohne Rinde gescannt wird oder ob die St/imme zum S~igen frei drehbar, fudert oder optimal ausrichtbar sind. Die Ergebnisse zeigen, dat~ die Ausbeute um 0.5% gesteigert werden kann, wenn einachsige Scanner durch zweiachsige ersetzt werden. Eine weitere Steigerung erm6glicht der Einsatz eines 3D-Scanners, allerdings nur, wenn das Rundholz zum S/igen optimal ausgerichtet werden kann. Die Ausbeutesteigerung betr~igt ca. 2% bei Messen mit Rinde und bis zu 4% bei Messen unter der Rinde.

Classification of crook types for unbarked Norway spruce sawlogs by means of a 3D log scanner

“…Oja et al 1998) will provide information about log mantle under bark, in addition to information about density variations inside the xylem, as opposed to optical scanners working on bark. Mongeau et al (1993) evaluated the capability of shadow scanners to observe the log crosscut shape, and Skatter et al (1998) extended the analyses to 3D and other scanner types. Scanners will calculate the bow height, and provide some algorithm to automatically deduct the yield diameter for sweeped logs (Anon 1999).…”

Variation des caractéristiques de la moelle des arbres de Gmelina arborea issus de plantations à croissance rapide au Costa Rica

“…This relationship can be suggesting that there might be a relationship between secondary growth of tree diameter and pith diameter. Many studies report asymmetry between the tree and the internal pith characteristics (Koch et al, 1990;Skatter and Gjerdrum, 1998). This factor has a notable effect on the number of boards with pith and can cause deformations owing to its association with reaction wood, lower wood density, and decreased mechanical resistance, among other factors (Dumail and Castera, 1997;Machado and Cruz, 2005;Moya and Muñoz, 2008;Skatter and Gjerdrum, 1998).…”

Detecting spruce and fir log diameter under bark by using shape and image data

“…Such an approach is subjective in the first place, leading to discussions between client and purchaser unless an independent grading organisation is involved. Additionally, it can cause estimation errors for the volume under bark especially if a considerable amount of bark is already missing (Oja et al 1998;Skatter et al 1998;Chiorescu & Grundberg 2001).…”

“…Edlund 2004;Oja et al 2004), for sawing optimisation (e.g. Skatter et al 1998;Nordmark 2005;Lin et al 2011) or for tracking logs through the sawmill (Flodin et al 2008). Bark detection based on the log contour data has not been reported yet.…”

“…They reported a reduction in bark assessment error of 50%. Several authors discussed the advantages and disadvantages of X-ray scanners that can physically measure the diameter under bark (Skatter 1998;Skatter et al 1998;Oja et al 2003). X-ray scanners usually have two or three fixed positions for measuring diameters around the log surface and can, therefore, model cross sections only as circles or ellipses (Skatter 1998).…”