Optimization from MPM Engineering Enables High-Tech Mill to Recover Grade Lumber from Small Wood
CHESTER, S.C.—Willamette Industries, Incorporated, in addition to being one of America’s giant forest products companies, is a major innovator when it comes to creating high grade products out of low grade materials. Timberline reported on the firm when, just four years ago, it was the first company in the nation to experiment with environmentally sensitive finger jointing glues, made from soybeans. Since then, the company has embarked on dozens of other, on-going initiatives aimed at improving the environment through greater utilization. One of those is now coming to fruition at Chester, South Carolina where the firm is beginning to operate a new, high tech sawmill that will produce grade lumber from material that was once either chipped or converted into lower-valued products.
Robert (Sandy) Trewolla, plant superintendent at the new mill, says that the mill’s production represents a tremendous value-added step forward for his operation. “You can’t do a better job of using up every last bit of value from a resource,” he commented to Timberline. “The fiber we saw was once used for garden timbers or chipped up. Now we’re making lumber, and excellent lumber at that.”
The Chester Sawmill, Sandy said, is designed to produce more than 38 million board feet of lumber annually with 95% being kiln dried, planed Southern Yellow pine and the remaining 5% being soft hardwoods. Seventy-five percent of the lumber is sawn from plywood cores generated at Willamette’s plywood mill which adjoins the new facility; the remaining 25% comes from green logs initially processed at the plywood mill’s log utilization center. The green logs, Sandy explained, are tree tops and other logs not suitable for peeling as plywood stock but still too valuable, in the company’s mind, to either chip up or otherwise dispose of.
It might be tempting to think that with the Chester plant’s mix of logs, Willamette Industries might go with a simplistic break down system, but that is hardly the case. The new mill is a state of the art manufacturing facility featuring advanced optimization by a leading small log optimization company, MPM Engineering Ltd, a Canadian firm. MPM cut its teeth on small log processing, and according to Ron Gillespie, head of sales and a partner in the firm, has more than 20 years of optimization experience.
At Chester, both cores and green wood are delivered to the sawmill via a series of conveyors. The cores are created as part of the plywood plant’s process; each is 8′ long and 5 1/8 inch diameter. The greenwood consists of tree tops and logs not suitable for the plywood process; a good deal of it contains sweep or crook. Greenwood is debarked at the plywood plant and then forwarded to the mill.
The fiber is bundled and stored until the sawmill needs it. A Caterpillar 950 handles the wood.
When scheduled for breakdown, the fiber is loaded into the sawmill using a deep pile infeed deck capable of handling about 300 cores. An unscrambler moves the fiber to the accelerator chain of the breakdown system.
Breakdown is accomplished using a CAE-McGehee SL2000 small log processing machine equipped with MPM’s scanning system which has been specifically designed to maximize yield from small logs. The SL2000 is capable of both straight and curve sawing. When running cores, the machine is on a fixed set with logs running through at the rate of 45 per minute. The mill utilizes its scanner optimizer to process green logs. While it is slower to process green logs than cores, the production rate remains substantial at 24 logs per minute.
Once sawn, lumber moves to a trimmer which trims both ends to remove defects and then onto the sawmill’s six bay sorter. The next stop is a stacker which will handle 12 courses of lumber per minute or 288 boards. Stickers are placed between each layer to facilitate drying. Lumber is dried to 19%(MC) in a 94 foot, double track high temperature kiln capable of drying 168,000 board feet per charge. It is then moved onto dry lumber storage sheds and held until run through a Coastal 49-6C planer.
While the planer is capable of processing 2000 feet per minute (250 eight foot boards), Chester’s system is presently set up to handle about 800 feet per minute, which is sufficient to process the mill’s output with plenty of room for future expansion.
Once lumber exits the planer, it moves to the grading chain where each piece is inspected and graded. The mill makes only 2×4’s, 2×6’s and 4×4’s. Willamette pulls grades #1, #2prime, #2, #3, and #4 on 2×4 and 2×6 lumber and #1, #2, and #4 on 4×4 material. The Southern Pine Inspection Bureau certifies the grading, which is done on National Grading Rule standards.
A true indication of the incredible increase in fiber value at the Chester mill is most evident at the grading line. Because all of the wood being run through the mill is from the center of the log or from tops and defect logs, it could be expected that a low grade of material would be extracted. Nothing is further from the actual facts, Sandy said. “Our grade recovery has been excellent,” he commented. “On 2×4 and 2×6 lumber, 85% of our recovery has been #2 and better. On 4x4s we’re seeing more than 90% grade as #2 and better.”
The graded lumber passes under a grade mark reader which identifies the grade marks and then trims, stamps, and sorts pieces into the bins dictated by the markings. When a full package of lumber has been sorted into a bin, a sorter haulout chain moves the lumber to a finished stacker for stacking. The lumber is then strapped, marked, and moved onto a 1 million board feet capacity storage area. Ninety-eight percent of the lumber is picked up by customers.
Sandy said he has been particularly impressed with the MPM Engineering optimization system as it works in conjunction with the CAE-McGehee curve sawing system because it is both efficient, and places a good deal of control within the mill. “The folks at Willamette spent a lot of time over the past couple of years selecting equipment designed to fill our needs,” Sandy pointed out. “And they did an excellent job. This has worked out very well for us.”
Sandy has been particularly pleased with the MPM Engineering’s software. It has the capacity to “capture” any run of logs running through the machinery in terms of the actual solutions that were developed for them. The mill’s managers can electronically change the parameters and see what quality and quantity impact those changes would have had on the lumber sawn from the run of logs. While other systems also allow this theoretical look at a run, Sandy said he particularly appreciated the fact that with MPM Engineering’s software the whole thing can be easily done at the mill by his experienced people. Changes can be made quickly and easily without the need to call in factory people. That’s partly due to the fact that Willamette employs people capable of learning systems. Sandy commented, that “MPM has worked hard to develop a package that is very user friendly.”
The new sawmill alone at the Chester, S.C. plant employs about 40 people and is forecast to produce 38 million board feet of lumber a year, mainly for the treating industry in the area.
Few firms in America can match the accomplishments of Willamette Industries in terms of maximizing value from the product it processes. Because making maximum use of the resource is environmentally significant, Willamette’s new mill at Chester represents a real step forward for the industry, one that other companies may want to emulate as they too strive to be responsible stewards of resources and improve public perception of the industry.