Softwood veneer scanning is all about accuracy, quality and speed. For high speed production mills, the mill that can make the best grading and clipping decisions and do it the fastest has a productivity advantage in this tough market. This is the challenge that is being met by Tolko Industries of Vernon, B.C., the second largest producer of softwood veneer in Canada, which recently upgraded its White Valley, B.C. mill using optimizing technology provided by Daqota Systems of McKinleyville, Calif., and Cloquet, Minn. As a result of a commitment to continuous process improvement and seeking out technology innovators, Tolko has become a world technology leader in softwood processing.
July 9, 2012 By Treena Hein
The lathe at Tolko’s White Valley mill peels veneer from several species of softwood logs, including Douglas fir, spruce, hemlock, pine and larch. A value is assigned to each type of grade, and a rotary knife cuts the veneer to width depending on the desired criteria. The goal of the clipping process is to get the most value from the veneer resource by accurately identifying defects and grade and clip placement. Accurate identification of splits, gaps, wane, voids, and species-specific defects is critical to the process.
Because Tolko’s lathe is configured as a “shotgun” lathe and is close-coupled to the clipper, clipper speed can have a more immediate effect on peel and scan speed than on a typical multi-tray system. Full sheets (54s) are scanned and graded at the highest speed while “flawed” and random-sized sheets are scanned and graded between 100-150 FPM slower. This dynamic makes it critical that the impact of handling flawed veneer be minimized in order to maximize plant output. This wasn’t happening well enough with Tolko’s original clipper optimizing and control system.
“We would try to make changes to improve the operation of the system, but it wouldn’t always do what we wanted it to,” says Ralph Dawson, Tolko’s veneer co-ordinator. “We didn’t know in advance what impact a particular change would have.”
Dave Conly, current Tolko plant manager, inherited the project when he took over for previous manager Troy Connolly. Conly continued the project and is already seeing important productivity gains.
|Tolko says with the Daqota system, they can make better decisions.|
Connolly encouraged the Tolko team to find an optimizer that could make better decisions and accurately identify a wider range of defects and grading criteria. If the system were designed correctly, it would enable them to optimize the value of the veneer sheets that are produced, and do so at possibly the highest production speed in the world. The system could be tuned by archiving images of the ribbon and enabling the clipping process to be virtually rerun offline, using new parameters, to see what the value of the ribbon would be if different clipping decisions were made.
“We were looking to improve our scanning process so that we could make more informed decisions,” says Connolly. “We believed that our old in-line veneer scanner was leaving opportunity (and profits) on the table.”
Besides making better clipping decisions, Tolko also wanted the system to handle flawed sheets better. In the plywood industry, cut sheets of veneer that have flaws can be turned sideways and used for plywood core material. According to Tolko’s electrical supervisor, John Jorimann, the old system could only identify flawed wood on one side. By improving how flawed sheets are detected and handled, less usable wood is wasted.
One of the other problems with the old system was that the lathe would sometimes produce a ribbon with cracks in it, requiring an operator to get involved and direct it to the green chain in order to avoid having partial sheets divert to the full-sheet stacker. There needed to be a way to detect and handle cracked sheets without requiring human intervention. Daqota developed some special detection and clipping algorithms for the scanner that solved this problem downstream at the diverter and stacker.
Tolko has a history of being very progressive in its use of new technologies, and the improvements it was asking for had never been implemented in a softwood mill before. Tolko needed assistance from a research and development oriented engineering firm that had experience developing the latest optimizing technologies. The company surveyed the market and saw that Daqota Systems had such technology and expertise.
To obtain the scan speeds and enhanced detection algorithms that Tolko needed, without compromising features and accuracy, Daqota proposed a major upgrade to its Q-Scan green veneer scanning and grading system. Q-Scan is a combination of hardware, software and detection algorithms designed for softwood and hardwood scanning and grading at high speeds. By developing and making full use of next generation technologies, including new optimization algorithms and new detection and grading features, and running the system at higher processing speeds, Daqota’s Q-Scan could be upgraded to revolutionize very high speed software veneer processing (up to 900 FPM).
The Daqota system uses colour scanning and complex detection algorithms to identify a large array of defects and grading criteria, and directs the clipping and cut sheet handling processes to minimize waste and reduce the number of randoms sent to the green chain. The system also performs a pre-clip analysis that takes into consideration the information that downstream equipment needs, and develops a strategy for how to accept or reject defects and clip the ribbon accordingly.
Daqota’s technology makes full use of much higher processing power both on the computer processor level and on the graphics processing level than do other veneer production optimizers, enabling more information to be processed with greater accuracy for defect analysis, grading and downstream handling analysis. Daqota’s new Q-Scan does all of the analysis and decision making at up to 900 FPM, in colour, and stores the information for post-scanning analysis.
“The new Q-Scan user interface is much easier and more manageable than our old system,” says Tolko’s Dawson. “We can watch the screen in the control room and see the decisions that the system is making. We can even pause the veneer and look at the defects close up and how each clip was made, while the system continues to run.
With the Daqota system, we can make better decisions. The parameters that we can tweak are more appropriate for what we are trying to do, and more logical regarding how we grade veneer.”
An additional feature of the Daqota system is the “Sandbox.” The Sandbox is a post-scan analysis tool that will allow Tolko’s process people to re-run veneer ribbons through a virtual model of the clipping system to see the impact, positive or negative, of making different clipping decisions. Using the Sandbox, the process can continue to be optimized by Tolko’s people without needing to get Daqota involved every time they want to improve performance.
Overall, the initial phase of the development project took about six months. When it was complete, Tolko reported that it had the most accurate and fastest veneer processing line in North America, and was able to reduce the randoms (random-sized strips) by some 60%, which makes the process of composing completed plywood much easier.
“The scanning resolution is considerably better than what we were running with our previous system,” says Connolly. “Our entire process was improved as a result of making better decisions. Now we can make clipping decisions based on what we know about the drying process, too.”
Jorimann explains: “The Daqota system sorts flawed sheets correctly, sending them to a specific bin in the stacker. Then, when the wood gets to the dryers, the good wood can be fed in first. This avoids plugging up the dryers with pieces that don’t fit easily.”
Dawson adds: “The sorts are cleaner going into the dryer. In the past, we were getting product put in the wrong stacks and that was causing inefficiencies. Now, more veneer is getting into the right pile, resulting in less downtime and a 1% to 2% improvement in our productivity.”
The new clipping strategy sends approximately 50% less veneer to the green chain (where random and trash pieces are handled), delivering more wood (wide random, flawed sheets and full sheets) automatically to the stackers. This keeps the line running faster and frees up manpower to do other things. Overall, the Tolko team estimates that the productivity improvements come along with a 5% savings in labour costs.
“We couldn’t have reached our goals without help from Daqota Systems,” says Jorimann. “The Daqota people on this job were the best that you could get.”
|Staff at Tolko were looking for ways to better identify a wider range of defects and grading criteria.|
From Daqota’s perspective, company president Tim Woodward says, “The Tolko team provided one of the best experiences and best partnerships we could have hoped for. Every member of their team is intelligent, knowledgeable, hard working, and invested in this project in such a way that greatly enhanced the successful outcome. They treated our team with great respect and provided an excellent production-oriented development environment. I can’t say enough great things about them and Tolko as a company.”
Tolko will continue to look for ways to improve its process. Maximizing recovery will become even more important in the future as the plant plans for handling smaller logs and shorter veneer ribbons.
Article provided by Daqota Systems and Tolko Industries.
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