Buildings, furniture, bridges, and musical instruments — all of these wood products start with the the same fundamental building block — the log. The quality of the log can make or break the final product, and this begs the question: are all logs created equal?
The Forest Products Laboratory (FPL) and the Northern Research Station (NRS) don’t think so. In one of FPL newest publications, Nondestructive Evaluation of Wood: Second Edition, researchers document different nondestructive evaluation (NDE) methods, including x-rays and ultrasounds, to assess and report on the condition and integrity of wood. These techniques help industry professionals make informed decisions about a wooden material without destroying it or compromising its structural integrity.
One of these NDE methods used for logs is laser scanning. Although there are many variations on this technology, each laser scanning system has two main components: a laser line generator (which projects a laser line onto an object), and a camera. The camera and the laser are separated by a measured distance, and the camera is aimed toward the projected laser line at a specific angle. Using the camera angle, the distance between the camera and the laser, and triangulation, the distance of the points along the laser line projected onto an object can be determined.
When scanning logs, a series of laser lines are projected around the surface of the log along its length — and the more lines, the better. By increasing the lines and decreasing the distance between them, the resolution of the scan is increased, and operators can get a more detailed scan of the log. A laser scanning system typically has lasers spaced 6 to 24 inches apart, but the Forest Service has developed an experimental, high-resolution, scanner with lasers placed 0.0625 inches apart. At this resolution, any defects on the log’s surface become obvious.
“Laser scanning is normally done just before processing,” writes Edward Thomas, NRS Research Scientist and contributor to FPL’s NDE book. “To effectively convert logs into lumber, their attributes (diameter, shape, length, sweep and taper) must be accurately measured.”
If the width of the first board cut from the log is too narrow, the grade and the value of the board is decreased. If it’s too wide, then too much wood will be wasted. In addition, by knowing a hardwood log’s taper and sweep, it can be positioned so that there is minimum volume loss from the “jacket boards,” the most valuable boards cut from a hardwood log.
The use of laser scanning technology has become an accepted and economical means of determining the size, shape, and features of logs and lumber. Newer systems can determine grade, yield, and value of a log, even before sawing. The FPL, NRS, and the Forest Service will continue to work with industry partners to develop new technologies to help maximize yield, decrease waste, and maintain the health and integrity of our forests. In this pursuit, every cut counts.