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An Edge On Scanning

At Elk Falls, rethinking the control systems for two recently installed optimized edgers has increased piece counts dramatically.

By L. Ward Johnson
Copyright 1997. Contact publisher for permission to use.

In the spring of 1995, the Elk Falls lumber mill at Campbell River, BC on Vancouver Island flipped the switch to start up two new Optimil optimized edgers. The units were part of a $16-million mill-wide upgrade, intended to revise log sorting and breakdown capabilities for processing smaller logs.

What was unique about the edgers was that they both were serviced by one scanner. Although this is not yet a common configuration in industry, it is in use in some plants which incorporate advanced computer technology. Having one scanner offers improved efficiency for the equipment and helps keep costs under control.

As part of the configuration at Elk Falls, both edgers were located in-line. After coming through the scanner, boards were either sent directly to the first edger or dropped through a gate and sent to the second edger. Board flow was reunited again behind the edgers, to continue the remanufacturing process.

OSB At first the idea seemed to work at the Elk Falls plant, but as the rest of the mill came up to speed, the edgers were unable to keep up. This mill cuts mainly for the export market, which means a wide range of lumber sizes and grades. The single scanning system simply couldn't feed both edgers to their maximum capacity and, at best, the two edgers were outputting only about 11,000 pieces per shift when they should have been doing much more.

In the spring of 1996, Mill Manager Ron McDonough and his staff decided something had to be done about the problem. They approached the Optimil people and asked them for suggestions. Optimil said they weren't happy with the situation either and suggested the entire edger optimizer system be revamped.

Together they worked out a plan to separate the two edgers so they were parallel instead of in-line, install separate scanning and computer controls for each unit, and switch the scanning and computer control programs to a Nanoose system. The revisions were completed last April and since then, not only has the bottleneck been resolved, but edger output has risen to over 18,000 pieces per shift.

Nanoose Systems Corporation, headquartered in Parksville on Vancouver Island, was started in 1990 by engineers Tony Silver and Lawrence Glaister. Both worked on software design for Kockums, but when the company moved operations to the US, Silver and Glaister elected to remain in BC.

At first they designed software for applications outside the forest industry, but when sawmill companies began coming to them for modifications to old Kockums programs, Silver and Glaister realized where their opportunities lay and again began designing software programs for sawmills. Glaister says they still get requests for updates on PDP 11 systems.

At present, Nanoose software systems are at work in more than 60 sawmills in Canada, the US and New Zealand. Working with systems integrators, the company provides mill-wide true-shape optimization solutions for log merchandising, autorotation, primary breakdown, cant optimization and edging. In the US they work with Trident Systems, while in Canada, their systems integrator is Optimil Machinery Inc. of Ladner, BC.

OSB Separating the two edgers and setting up an individual scanning system for each allowed the Elk Falls plant the option of reallocating edger functions. It was decided edger number two should handle side boards from the Chip-N-Saw, while the first edger would take wany pieces from the center cants for re-edging, and pieces from the trimmer optimizer and graders that required remanufacturing.

Edger one was to be fed by a lug chain, while a standard chain affixed with catches would feed edger two. A lug chain requires synchronization between loading and unloading, while the catch chain can be loaded any time. The main concern is that the boards are stable as they pass through the scanner.

Dean Stubbs, systems optimizer at the Elk Falls plant, says once the flitch has been scanned, the Nanoose system goes to work. Each edger has its own computer, which takes the true-shape, laser-scanned, three-dimensional image and attempts to fit every possible combination of mill-defined board products into every valid position in the flitch. The capabilities of the system allow the mill to set up precisely the match it wants, based on wood supply and machine centre characteristics, as well as current market conditions. The equipment is capable of more than 100,000 product fits per second.

"The system tries to get the widest, longest piece possible from a 4x8 to a 1x4, in 1'' increments, according to dollar value tables. The optimizer software considers trimming the piece, edging it, resawing it to a thinner size or, if it is thick enough, a multi-layer option. For example, from a 4'' side flitch, it will optimize to recover a 2''-thick piece on the bottom, and a second 1'' or 2'' piece on the top. The resulting 4'' piece can then be resawn to recover the two thinner pieces." Stubbs says the Nanoose system can produce up to five per cent more lumber recovery, compared to optimization systems using less advanced scanning techniques.

"The changes have made a significant difference in the performance of our edger optimizing centre," says Stubbs. "Before the change, we had difficulty achieving 11,000 pieces a shift from both; now we routinely process over 18,000 pieces a shift. We test the system every morning by processing pieces chosen at random and reassembling them, and we have never found anything wrong with the optimizer's decision. I can assure you, we are very happy with this system," says Stubbs.

The Nanoose system utilizes four computers to run the Elk Falls edgers. The four are linked together via an Ethernet system which utilizes dual 133-MHz Pentium Pro processors running under Windows NT. Upon arrival, the package is complete with pre-installed software, monitors and printers.

In looking ahead at the direction technology is taking, Lawrence Glaister says the next big jump is likely improved scanning systems. "Curved sawing is a hot item in the industry right now, but overall it doesn't seem to offer much gain. Studies show a gain in recovery of three per cent or less from curved sawing and that may not be enough to warrant the cost. You can get seven per-cent increase in recovery with a two-sided canter on a Sharp chain, followed by a canter optimizer, so the three per-cent recovery gain you get from curved sawing pales in the face of this configuration.

"I think the next big jump is going to come from better true-shape scanning and defect scanning," Glaister says. "The next generation of scanners will definitely look inside the log and assess defects before a sawing decision is made. There are already experiments with CAT scanning (computerized axial tomogram) although radiation is a problem with that technology. But something along the lines of, say, magnetic resonance imaging ' MRI ' may be just what we are looking for. This is proven technology and if it does the job safely, efficiently and cost effectively, we could see it in the mills soon."

OSB The equipment is basically European in design and the mill can handle lengths up to 9 metres (30'). Annual lumber production is about 20,000 m3 (8 million fbm), but the mill operates only on one shift, which seems to be typical of small rural mills in France. While small relative to North American mills, Pierre Garmier observes that the objective "is not to maximize production but to optimize the grade and size recovery. Log costs are high as the price must be negotiated with each owner."

Glaister notes that technology is changing very quickly and mills have to keep up if they want to stay in the business. "We sell technology, and as a small company it's relatively easy for us to keep up. It's more difficult for the mills, however, because a change in technology usually means equipment changes - often an expensive proposition. But it is a competitive world; you either keep up or get left in the dust - and that isn't an appealing alternative."

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