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Irish Sawmill Turns to USNR for New Log Line: USNR Blends North American, European Log Processing Technology
Murray Timber Products – Irish Sawmill Turns to USNR for New Log Line
Date Posted: 3/1/2008
The operating philosophy of North American sawmills generally is to treat every log as unique, but European mills tend to pre-sort their logs in the yard for continuous batch processing to achieve comparable production.
So when Murray Timber Products of Ballygar, Ireland came to USNR for a completely new log line in December 2005, no one predicted that it would result in a new breed of mill operating with a hybrid log processing philosophy.
Murray Timber operates at speeds slower than North American mills, but it is able to achieve comparable production. All logs are pre-sorted to within 1 centimeter, so the mill can run continuous batches of homogenous material with very short gaps between pieces.
The mill was replacing a CSMI (USNR) log line that was destroyed by fire. “The CSMI line gave us fantastic service, and since USNR produces even better equipment now, we could see no reason not to go with USNR,” said John Murray, production director. “USNR is the Rolls Royce of sawmilling equipment.”
Murray Timber purchased a new USNR primary and secondary breakdown line equipped with 3D Smart TriCam scanning and the new MillExpert Integrated Processing Line (IPL) optimizer.
A new hybrid approach blends the speed of pattern processing with the recovery of optimized sets. “We pre-sort our logs by diameter or pattern into 15-20 sorts, depending on length, which are then batched for production runs up to three hours long,” John explained. “In these runs we hold a centerpiece pattern and vary the sideboard products to achieve the best fit per log.”
USNR’s first pattern-specific optimizer, the IPL (Integrated Processing Line), was developed to allow the mill to combine the high throughput of pattern processing with the increased recovery of sets optimized for each individual log’s 3-D shape.
The IPL allows the basic sawing pattern to stay the same throughout a batch of logs. It maintains a consistent center cant but allows variations in the widths of profiled sideboards; it also allows sideboards to be symmetrically sacrificed (first outer pairs, and then, if necessary, inner pairs) as needed to achieve acceptable finished material. No edger is needed.
“USNR’s MillExpert optimizer software is comparable to the best and easier than the rest,” said John. “Even the upgrades have been very easy.”
Logs are initially scanned by 3D Smart TriCam sensors, then move through a quad roll log turner to be automatically rotated for optimum recovery; they proceed down a single length infeed to a horizontal chipper, creating a two-sided cant.
Murray Timber’s European-style linear log line features three cant turners, three profiling modules and four scan zones. The scan data images and resulting optimizer solutions are relayed from station to station successively down the line, enabling just one operator to run the entire line from logs to boards.
The two-sided cant is then scanned and turned 90 degrees by a ring turner and lands on a rollcase on the way to the canter infeed. The scanned image is sent to the cant optimizer computer to develop the solution. The two-sided cant is then fed into a second chipper with a skewing infeed that creates a four-sided cant. The four-sided cant is scanned and turned again before proceeding to double profilers.
The profiled cant makes its way to a USNR Quad Arbor Saw Box with guided saws to produce sideboards. The profiled sideboards exit to a sideboard dispatch table and transfer to one of the mill’s two existing sorters.
The remaining center cant is turned a third time and flows through another profiler, a versa gang also with guided saws, and an outfeed module. The center stack continues on with the option of being split at the splitting saw module that makes the final cut before boards exit to the mill’s second sorter.
Processing Sitka Spruce
“The new line has already achieved the levels of the sawmill it replaced, which was in production for 11 years and was highly tuned,” said John. “But it’s still in the shakedown period and has even more potential.”
Murray Timber is a family owned operation formed by Paddy Murray. His four sons have senior positions in the company’s two mills, which are located in Carlow and Ballygar. The company was started in 1978 with four people; it now employs more than 140.
The USNR line supplied to Murray Timber processes 99% Sitka spruce with top end diameters from 4-14 inches cut to lengths ranging from 8-16 feet. The mill produces a variety of lumber products, including pallet, fencing and construction lumber products.
“We’re a one-stop shop with 2,200 different products,” said John. “Ninety-seven percent of our production is sold on the domestic market, which is a small country, so we must cater to a wide range of needs.”
“I absolutely recommend this system, and USNR, to other mills,” said Murray, who has worked at the company for 16 years. “This USNR equipment is extremely strong and resilient. We get good accuracy, through-put and recovery as well as efficient manpower utilization.”
“We are incredibly satisfied with the USNR system,” he added.
USNR Quad Arbor Saw Box Provides More Control
USNR has installed over 30 Quad Arbor Saw Boxes over the years, and continuous design enhancements have resulted in a highly efficient, accurate machine. Recent improvements provide even more control over the product during processing.
A Quad Arbor Saw Box is a circular saw alternative to a quad bandmill. It typically features two pairs of horizontal fixed-position arbors that drive one or two saws (per arbor). But because the arbor spacing is fixed, the saws on the lower arbor do the majority of the sawing work while the upper saws engage only on larger diameter logs. This leads to uneven saw wear, which in turn leads to lower quality sawn faces and saw alignment problems.
USNR’s Quad Arbor Sawbox uses a unique arbor arrangement to alleviate this problem and achieve a balanced depth of cut. The top saws are positioned upstream of the bottom saws, leading the cut. This permits the top arbor saws to pivot down in front of the bottom saws, to equalize the depth of cut for various log sizes; this provides a key advantage, resulting in higher feed speeds, lower sawing deviations and reduced kerf.
The result is that both top and bottom saws do nearly the same amount of work and therefore wear at about the same rate. The top arbors shift by pivoting around the axis of the bottom arbor, ensuring that a minimum distance is maintained between the top and bottom saws.
Recent enhancements to the Quad Arbor Saw Box provide even more control over the product during processing. Steel side rolls have been placed inside the machine on linear positioners and roundways to better support the piece as it exits. Side tire supports were removed, allowing for the addition of an extra press roll on the outfeed. These improvements provide better control of the piece as it moves through the machine.
Many mills today are adding profiling capabilities to their upstream processes, which eliminates the need for an edger. Boards emerge from the Quad Arbor Sawbox ready for trimming, sorting and drying. When coupled with USNR’s powerful MillExpert optimization, this machine center is fast and accurate, maximizing value and throughput.
Low maintenance costs, high quality sawn faces, and a low-profile footprint are just a few of the advantages of USNR’s Quad Arbor Sawbox.
(Editor’s Note: USNR will exhibit at the Wood Technology Show March 12-14 in Portland, Ore.; visit the company’s exhibit at booth #533 to learn more, call (800) 289-8767 or visit www.usnr.com.)
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