The Tolko sawmill in Merritt, BC is currently seeing approximately 80 percent bug kill in its log diet of Western SPF and green Douglas Fir delivered in 8 to 20 ft. random lengths. The graders had to be overly conservative when grading to stay in control of below grade. This resulted in a large amount of above grade in finished packs, and lost revenue.

The mill’s Newnes-McGehee’s Linear High Grader (LHG), installed for geometric scanning in October 2004, was upgraded recently to handle the problem. New processors, water-cooled x-ray source and detector, 4 multi-channel vision sensors, LED light bars and a new electrical panel were installed. Tuning the system to the mill’s requirements and training mill personnel completed the job. 

With the LHG’s modular design, upgrades are performed within the same scanner frame. A “gate” allows production to continue while the new hardware is being installed. Over the 2 weekends of hardware installation, the mill experienced no disruption in production. 

With graders, the mill was limited by speed and the number of high grades it could pull from beetle killed pine. With the LHG grading capability, the mill has the flexibility to pull all the high grades. It has also increased throughput speed by 15 percent, and gained control of off grade, so it can realize the full value of its products. 

Don Willson, Tolko Merritt’s planer mill Quality Control Supervisor made the following comments. “Before the upgrade, we were limited to the number of grades we could pull – now it is virtually limitless with the graders only grading for a couple of defects. We can pull any grade at current line speeds and stay in control.” 

The LHG also allows the mill to make cut-n-two decisions, increasing the high grade yield.