Acoustic log tool increases returns for NZ sawmill
from Friday Offcuts article www.fridayoffcuts.com
Waimea Saw millers in Nelson, New Zealand, has seen an increase in returns, reduced costs, wastage and produced additional out-turn of structural quality timber, thanks to the installation of a new acoustic log grading unit.
According to Waimea’s Operations Manager Kent Gibbons, the introduction of the new timber grading standard NZ3622 and market demands forced the Nelson operation to move away from visual grading and install a Stickman sonic grader in 2006 in order to machine stress grade their lumber output. The company quickly identified that there was still a missing link in the process – the logs needed to be tested for stiffness (to determine if they were building grade or not) before they were sent through for sawing.
“We found ourselves cutting timber to what we thoughts would produce MSG and then being disappointed with the result, and also the reverse situation where timber was processed into what we thought would be downfall grades, but they turned out to have a higher sonic reading than expected. It became obvious that what we needed to maximize MSG lumber out-turn was sonic information from the whole logs”, Gibbons said.
In September 2007, the company installed Fibre-Gen’s new, automated Hitman LG640 and as a result, successfully removed the guesswork from the grading and milling process. The unit is positioned on the debarker out-feed, allowing Waimea to sonic grade every log into the green mill on a daily basis. As each log exits the debarker, the length is measured, the acoustic tool strikes the log while it is still moving, then automatically sends the results through to the operator’s cabin.
Logs are queued on the in-feed deck, and as each rolls into the machine in-feed, its sonic reading is displayed on the operator’s control panel. Gibbons says this gives the operator the advantage of being able to adjust the cut pattern to maximize MSG output. Waimea have made at least a 3% gain in MSG recovery since installing the LG640, which equates to a significant improvement to their bottom line. Waimea is currently conducting trials on log diameters to determine the optimum log mix for processing to achieve their machine stress grading targets.
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