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February 2007 - The Logging and Sawmilling Journal

SAWMILL TECHNOLOGY

X-RAYING THE LOGS

A visit to a sawmill operation on Finland’s west coast clearly shows that making better cutting decisions and achieving optimum breakdown decisions—in this case with Rema x-ray scanning equipment— is just as vital there as it is in Canadian mills.

By Alan Froome

In an industry that continues to see a lot of change—and a consolidation of companies on the equipment supplier side—it’s reassuring to find that some companies don’t change, though their technology continues to evolve.

When researching the recent article about the first log scanners in Canada and the United States (please see September 2006 Logging & Sawmilling Journal) it was significant to note that RemaControl AB was not only one of the first companies to install a system in North America some 35 years ago, but that it is still very much in the same business today. This, unfortunately, does not apply to many of the pioneering scanning companies on this side of the Atlantic.

The Luvia operation is typical of Nordic sawmills in that it runs on finely sorted logs—there are 90 sorts at the mill.

In fact, RemaControl AB was founded way back in 1954 and is still based in Vasteros, Sweden. As a follow up, it’s interesting to see what Rema is doing in 2007 and in which direction scanner development has taken the company.

Rema has a log x-ray scanning system of special interest, says Mathias Karlsson, sales engineer at the company. Karlsson says that Rema currently has three of its x-ray systems in operation, two in Sweden and one in Finland.

The RemaLog XRay system in Finland is at Luvia Saha Oy, just south of Pori, on Finland’s west coast. With the kind permission of managing director Harri Huhtimaa, Luvian sawmill supervisor Petri Salminen was able to provide some details about the system, and the mill.

The Luvia operation is typical of Nordic sawmills in that it runs on finely sorted logs—there are 90 sorts at the mill.

But making the optimum breakdown decision for each log is just as vital here as it is in a North American mill running on largely unsorted logs. The ability to scan a log for internal features, defects and knots at this early stage in the sawmilling process, and make better cutting decisions downstream, can be a big advantage in terms of overall mill recovery and profit.

Luvia Saha uses two scanners side by side at its log sorting station. Reflecting the mill’s northern location, both scanners at Luvia are housed in a heated building. The building itself has wall panels containing lead to protect personnel from the x-rays.

The Rema XRay system scans logs for grade, and the system software uses this information in conjunction with data from an adjacent Rema laser/camera scanner installed earlier, to sort the logs.

	The scanning equipment at the Luvia mill (left). The log bark scanner is the grey frame and the x-ray scanner is the red frame. The ability to scan a log for internal features—and make better cutting decisions downstream—can be a big advantage in terms of overall mill recovery and profit.

This older scanner provides true diameter (under the bark) and basic shape and length information. The 3D system, called RemaLog Bark, is also interesting in that it uses what is called the Trakeid method of measuring the external log shape with the bark on.

This method was developed and patented by the Swedish timber research institute, STFI. The system scales the bark thickness without relying on any predetermined bark tables, using six lasers and four cameras to scan logs at speeds up to 590 feet per minute.

The Rema scanner controls and computer equipment, plus two 160 KV power supplies for the pair of xray sensors, are housed next door with heating and air conditioning to provide a computer-friendly environment. Rema says its x-ray system requires an ambient temperature between 15 and 25 degrees C.

Red and green lights above the door indicate when it is safe to enter the scanner room. The xRay scanner, with its red frame, looks much like any conventional type scanner, with two heads positioned at 45 degrees above the conveyor and the two x-ray guns located below inside metal boxes, to protect them. The x-ray sensors themselves are supplied to Rema by a British company.

The log conveyor is a standard continuous chain flighted type, with the chain and the flights filtered out electronically by the scan computer. The x-ray system at Luvia is used primarily to scan each log for the number of knots, their size and the space between growth rings. Without giving all the company secrets away, Salminen says that this data is used to basically sort the logs two ways: best quality and lower quality.

The computer display looks much like a hospital x-ray picture—with shades of black and gray—and the display graphics can be demonstrated using captured log scans. Knots and splits were clearly visible on the screen in two directions. The space between growth rings is used to define wood density and therefore its quality and end use. Knot location and knot size is also a factor in deciding how logs are cut.

As a rule of thumb at Luvia, tight ring wood is usually used to make thin boards, flooring and profile siding. Wide spaced ring material is generally used for the larger size wood, the equivalent of squares, timbers, and 2x4s.

Their overall experience with the system has been positive, Salminen says. “We have been very pleased with the x-ray system and our customers like the more consistent quality of the products we ship them. In fact, if the system is down for some reason, we tend to shut the sorting line down while we fix it.” Salminen points out that the system is, in fact, seldom down.

Since everything is cut to order at Luvia, they literally have hundreds of different products. Salminen is responsible for the scheduling to meet the individual orders.

Rema says its x-ray system can also separate log species and scan for diameter under the bark, but the Luvia people prefer to use their older Log Bark unit for this function.

From a cost point of view, Rema says that an x-ray system, including scanner, software, electronics, cabinets, cooling system and power supplies, sells in Europe for approximately 450,000 Euros ($585,000 US).

The Luvia sawmill layout is like most in northern Europe, except for its use of x-ray log grading. It is one of the largest privately owned sawmills in Finland, with ownership in the hands of the Huhtimaa family. Production last year was around 230,000 cubic metres of rough and planed wood. It employs 120 people and the sawmill runs two eight-hour shifts a day.

To maintain this production, the log sort line is run for 1-1/2 shifts and lumber sorting is run between 2-1/2 and three shifts. The sawmill processes around 15,000 logs a day through its two canter lines.

	The Woodeye grade scanner (left) at the exit from the HewSaw, looks for wane. A kiln charge (top) ready to be moved into one of the mill’s 16 chambers on site.

The company has its own logging division and contracts 15 logging machines year round to keep the yard full. Logs range from a 100-millimetre to 500-millimetre top diameter and from three to six metres long, with 70 per cent spruce and 30 per cent pine. Logs are bucked in the forest by logging equipment and do not arrive tree length at the mill.

The sawmill comprises a 90-bin Tahka log sorting system with metal detector, running at 490 feet per minute, with sorting by quality (as described above) and size, mostly four to 10 millimetres between top diameters, with some critical sorts only one millimetre apart.

From yard storage, the logs are carried by mobile loaders and enter the sawmill
building on two decks, for debarking by two Valon Kone machines. In the mill,
smaller logs are processed by a HewSaw line and larger sizes by a Linck canter line.
All logs are processed top first through the Linck line using an automatic Tahka
turntable device. Both canter lines are run by a single operator, who overseas their
operation with an array of video monitors.

Automatic log turning on the Linck line is run by a laser/camera scanner, and a Woodeye grade scanner, at the exit from the HewSaw, looks for wane. Rough boards from each line are even-ended and pass through a single Heinola length trimmer before sorting by two side-byside drop bin J-bar lumber sorters, one 40 bin and one 30 bin. The centre cants produced by the Linck line are not length trimmed.

The mill has 16 kiln chambers on site. The kilns handling rough lumber are heated by 120 degree C hot water piped from a bark burning boiler. Lumber is normally dried to 16 per cent moisture content before passing through one of the two on-site planers. Custom profiles are produced by a Weinig Waco Maxi planer/ moulder running at 980 feet per minute and flooring is produced on a slower machine. Siding from the paint line is electrically dried on site.

Approximately 85 per cent of the mill’s products are exported, all over Europe and to North Africa and Japan. The mill specializes in custom profiled siding for homes and even offers it prepainted in a variety of colours.

This page last modified on Saturday, July 21, 2007