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Better log breakdowns

Weldwood’s efforts to get better log breakdowns at its 100 Mile House mill have received a boost with a scanning and optimization equipment upgrade.

By Jim Stirling

Fibre supply and sawmill design are joined at the hip. For Weldwood of Canada Ltd’s 100 Mile House operations, they are also the faces that must be stared down. Most sawmills in the Cariboo region of interior British Columbia have their wood delivered directly off the stump to the mill yard.

Weldwood’s 100 Mile House mill will be able to use information from the new Porter scanning system to make more accurate decisions on log breakdown, and allow production of more boards with higher grades.

But fibre for Weldwood’s mill in 100 Mile first goes through a sorting and high grading process. Weldwood wants to ensure the right stems go to the right processing plants in the region, which also includes company mills at Williams Lake and Quesnel. The process includes the removal of peeler stock and means there is much company wood movement around the Cariboo.

The residual or extracted fibre directed to the 100 Mile mill is SPF, with up to 10 per cent balsam and a similar percentage of Douglas fir tops. But—and herein lies the problem—an estimated 30 per cent of wood entering the mill yard possesses cat faces and other log defects.

The recent installation of the latest generation of Porter scanning and optimizing systems on both the mill’s lines is an initiative to solve the dilemma. “With this true shape scanning system, we’ll be able to see those log profile characteristics a lot better and position the logs with the least impact on lumber,” says Don Johnson, production manager for Weldwood in 100 Mile.

The recent equipment changes in the mill will help 100 Mile House work better with cat faces and other defects in its logs.

The Porter RT3 true shape scanning system replaces the manufacturer’s RT2 system installed in 1994. The 100 Mile operation benefitted from an earlier RT3 equipment installation at its sister mill in Quesnel. They were able to update the Quesnel experience into a better simulation package to justify the returns the operation anticipates, explains Johnson. “The true shape system uses laser scanning technology to give accurate descriptions of the outside surface characteristics of each log, its defects and anomalies. We’ll be able to use that information to make accurate positions for breakdown.”

The system scans the logs for rotation first and a second time for cutting head position, he adds. Johnson says the mill expects a five point improvement in recovery overall in the plant and anticipates an approximately two per cent grade uplift. Before, the effects of a cat face and defects could show up on more than a single piece of lumber, affecting the grade on both.

The new system should confine and reduce defects to one piece, allowing production of more boards with higher grades. Installing additional spike feed rolls to better hold the logs The chip ‘n saw line with double length infeed was handling between 7,200 and 7,400 logs per eight hour shift (two daily), while the USNR canter quad with standard length infeed had a typical throughput of 4,000 logs per shift depending on wood size. The new scanning system was installed on the chip ‘n saw line during an intensive three day holiday weekend when the mill was scheduled to be down.

The same approach was adopted later for the canter quad line. In both instances, some preparation electric wiring was possible prior to system installation. “Porter does a good job at start-ups and we were looking to a user friendly and comfortable transition,” says Johnson. The production staff is familiar with Porter systems, although the new system features some different human-machine interfaces. “The maintenance guys will have to learn how the new system operates,” says Johnson.

The RT3 system includes more comprehensive troubleshooting and reporting features. Adjust- ing flow patterns in one area of a mill has repercussions elsewhere and Johnson expects more work will be required in the mill’s back-end. One of the two trim lines has been upgraded and Johnson expects TechforServices of Kamloops will again act as project co-ordinator for modifications to the second line. It includes more accurate fencing to help smooth out lumber flow, says Johnson. “The scanner installation work positions us into the next generation,” he adds. Weldwood 100 Mile has also been working on its three older 100-foot Moore dry kilns.

They upgraded the heat coils and re-clad and re-plumbed the kilns to get better control of their hot oil system, says Johnson. “It’s worked well.” Fans are being upgraded to achieve better heat distribution throughout the kilns. “Our intent is to have two or three more charges a week in the winter months. We’re running about 13 to 14 and we want to up that to 16 to 17 charges per week. I believe we can do that.” is also part of the $1.86-million project. The additional feed rolls—along with more variable frequency drives—should also offer throughput advantages, says Johnson.


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