The X-Ray Lumber Gauge - A New Machine Grading Process from North America
Gerald A. Ziegler, Ph.D.
ABSTRACT Machine-graded lumber products have been manufactured in North America since the 1960's using a process which measures the flatwise-bending stiffness of the lumber. The strength properties of these products are derived from both the average and minimum bending stiffness along the length of the lumber, and a size limitation of edge knots determined by visual grading. A new machine-grading process, called the X-ray Lumber Gauge (XLG), was developed in the late 1980's. This process determines the density profiles both along the length and across the width of the lumber by measuring the attenuation of X-ray radiation passing through the material. Since knots are generally twice as dense as clear wood, the size of the knots and their location are determined within the lumber. The density information is used in algorithms that predict the strength and stiffness of the material. Both machine-grading processes utilize daily quality control tests to define operational machine settings and ensure product performance for each machine grade. The correlations between the measured parameters for each process and the mechanical properties of the lumber are compared in this article.
Publication Source: WCTE '98 - 5th World Conference on Timber Engineering, 1998 August 17-20, Montreaux, Switzerland.
Vol. 2, Pages 632.....
Publisher: Presses polytechniques et universitaires romandes - [Homepage]
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