Compact, fast, accurate solution
SYNERGY IS defined as cooperative interaction that creates an enhanced combined result. A recent synergistic solution was created at Stimson Lumber’s operation at Tillamook, Oregon, when the company chose a primary breakdown configuration that merged designs of product lines from the USNR family. The result is compact, fast and accurate.
The Stimson mill at Tillamook is predominantly a stud mill. The primary line utilized manual processing techniques, so the primary goal of the project was to employ more advanced technology to recover greater quantity and quality of lumber.
Jeff Webber is vice-president of operations for Stimson, based at its headquarters in Portland, Oregon. After studying different installations, different vendors, and different product mixes, he says, “At the end of the day we were convinced that the USNR system was the right one for us, for our log characteristics and what we wanted to do.”
Jeff explained that the solution they chose for this project incorporates a compact sharp chain positioning infeed system with side chipping heads, and cants are processed downstream at the mill’s existing horizontal resaw.
Positioned for accuracy
This configuration was chosen because it will handle the specific characteristics of the mill’s log diet, with its proven design for positioning accuracy and to maintain control of the log through the cutting tools. This is a very high piece count machine, capable of operating at 600 fpm and processing 24 pieces per minute.
The USNR supply includes the log feeder, positioned at the last step of the log loader to facilitate precise gap management between logs. Once loaded on the vee-flight chain, each log is scanned for defects, turned, skewed to position, thumped on a sharp chain, and a final scan is performed before processing - all within a very short distance. After the first scan a reciprocating quad roll log turner actuates the turn solution. Then the positioning infeed takes over the final log position adjustments by skewing the log end to end. This feature offers a big advantage allowing the line to position for specific log defects to achieve maximum recovery.
The skew is accomplished with two sets of centering rolls fitted with linear positioning cylinders. One moves the front end of the log left or right, the other moves the back end left or right. Once the log is in position the overhead pressrolls come down and thump the log onto the sharp chain. Then it is scanned again, and the system has the capability to move the chipping heads to make further adjustments before processing.
The attributes that make this design unique is that it is compact and simpler than an extended length infeed, it operates at high speeds and is extremely accurate. With this infeed concept there is no transition into the canter, so there is limited opportunity for the log to lose position prior to processing. This design will handle small to medium sized logs.
The optimization system Stimson selected is the MillExpert platform with Smart TriCam lineal scanning. From the first scan it creates a dense 3D model of each log. MillExpert’s Log Turner Optimizer and Log Optimizer work together for optimal turning and positioning to achieve the most valuable breakdown solution. Once the log is turned and skewed a second scan is performed to confirm the position of the piece, and the log optimizer finalizes the breakdown solution based on any discrepancy between the optimal position and the log’s actual position.
With the appropriate log diet, these compact infeed systems have an advantage over traditional extended length infeed systems because the logs are positioned onto the sharp chain in a very short distance, scanned for the breakdown solution and then proceed on the same conveyance into the cutting devices.
Detecting the turn
A particularly valuable feature of MillExpert log optimization is the turn detector. The turn detector allows users to monitor how well the rotation system is doing on every log, and provides reports that can indicate when problems occur. With the turn detector feature the mill personnel can easily monitor the performance of their positioning system and tune it, as required. To utilize the turn detector feature, a second scan must be taken after the log is positioned. Turn detector reports on the final rotation that was achieved.
Jeff Webber is pleased with the performance of the line. “It’s exceeded our expectations. We assumed some recovery improvement, which is why we did the project. We did not assume any productivity improvement because we thought we had other constraints in the mill. But we did get more productivity, so that was a bonus, and our (lumber) quality is better.”
“This is the best project I’ve ever seen in my 30-plus years. Everything just fell into place. It was on budget, it was on time, and the performance was better than expected,” Jeff says.
Now, Stimson plans to turn its attention downstream.
“Because this machine has a lot of production capacity that we’re not utilizing, we’re going to work in the rest of the sawmill to figure out how to tap into that capacity.”