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Timber Processing: Cutting Technology

Major filing room upgrades are impacting mill operations in big ways. Linden Lumber in Linden, Ala. and the Cowlitz Stud mills in Randle & Morton, Wash, are using Si-monds Automatic Bandsaw Levelers and Saw Control.

These plants undertook the upgrades from leadership positions: Linden as a top notch producer of Southern hard­woods, the Cowlitz plants as very well regarded high volume Western SPF mills. Both companies have long histo­ries as successful competitors in the de­manding export markets.

According to Ivan Allday, production superintendent (and head filer) at Linden Lumber, the filing room became a mission a couple of years ago. Management mapped out a strategy of “reducing kerf and target size, getting better yield,” says Allday. We spent a year and a half get­ting new equipment on line and testing it.”

Use of automatic band saw levelers has become routine in mills focused on accuracy. “The leveler has allowed us to reduce kerf and eliminates some of the human error,” states Allday. He notes that it’s become routine at Linden to put a saw on the leveler at the end of the sec­ond shift and let it run unattended until the day shift arrives. When asked about reliability, he comments, “2,500 running hours and all we’ve done is change a light bulb.”

The Saw Control unit is designed to report on the actual performance of the band saw blade while it’s in the cut. It uses a displacement probe to monitor de­viation and vibration in the saw, then an­alyzes the signal to give the sawyers feedback if a saw is overfed or underfed. It displays real-time saw performance on a control unit in the filing room, letting the filers analyze problems while the saws are cutting.

The impact of having access to this in­formation is far reaching. Once the sawyers know how hard each saw can be pushed in each cut, real gains in produc­tion are possible while maintaining or improving quality. “Our Randle plant has had substantial production gains in the last four months, at least half of it as a re­sult of the levelers and saw control,” says Charlie Allen of Cowlitz (Randle was the first of the Cowlitz mills to have levelers and saw control on line). “We’re seeing more consistent sizes at the planer and holding better tolerances,” he adds.

Linden’s Allday confirms that, “Saw control is one of the best information tools we’ve got. We’ve experimented with tooth shapes, tire lines and so on to find the best. We’re making better lum­ber than we’ve ever put out and a lot has to do with reducing the deviation from the saw control.”

Making objective decisions about how to put up the best saws is one part of the process, another is evaluating new equip­ment brought into the filing room. In sev­eral mills, including the Cowlitz plants, the saw control system has been able to demonstrate on paper the effect that auto­matic leveling has on band saw perfor­mance. Saws can be run and recorded prior to leveling, then again after.

The results of these evaluations have been unanimous—in each case automatic leveling has become part of the normal filing room routine. Allday states, “The leveler has just become part of the sys­tem, like a profile grinder.” Linden has used the saw control to evaluate other fil­ing room investments as well. In some cases it has proven machines will pay off, in other cases that they won’t.

A major key to the success that both Linden and Cowlitz have had with the saw control is building a team of users at the mill. When all of the key disciplines (filers, sawyers, maintenance, managers and quality control) have learned how to use the system they can begin making de­cisions based on common objective in­formation.

According to Allen at Cowlitz, his staff has been able to identify problems and measure their success in fixing them. “More than anything it lets us see what effect the work we did had,” he states. “The system has shown us the difference between the older mechanical strain mills and the newer air strain mills, and how much better the newer ones are. That will influence what we do in the future. ” At both Linden and Cowlitz the saw control has pointed to some specific problems with bandmill bearings or saw guides. Getting early reports on intermittent bearing problems can prevent the creeping decline in saw performance that usually precedes a failure. It will also prevent the un­scheduled downtime that a failure causes. A bearing beginning to wear and get sloppy will put a very iden­tifiable signature on the saw control unit in the filing room and make ev­eryone aware long before the bear­ing goes out.

The saw control reports the posi­tion of the saw, relative to the guide, constantly in thousandths of an inch. This gives a concrete measure of how accurately guides are machined and installed, and how much guide wear is present on each saw shift. By shifting guides with the mills idling we can also see how true the guides move.

In several cases we’ve seen guide ways that were worn badly enough that shifting the guide caused the saw to lead in or out of the cut. In these cases saw performance is actually im­proved by raising the guide all the way up, aligning it, and leaving it stationary.

Getting solid, objective information is the key. Allday says, “Where we’d have an alignment problem we can point it out to everybody and correct the problem, not make it look as though it was a problem coming out of the filing room.” Allen adds, “Payback is almost immeasurable. It affects how people do their jobs, taking some of the questions out of the process. It helps people measure what they’ve done.”

Excerpts from Timber Processing

December 1994 Timber Processing