Integrated vision system helps speed production, maximize efficiency at Pleasant River Lumber
A family-owned Maine business with four generations of experience in the forest products industry, Pleasant River Lumber produces more than 100 million board feet of spruce dimensional lumber and eastern white pine annually from its three mills in Dover-Foxcroft, Hancock, and Enfield, Maine. Pleasant River Lumber prints an American flag and the grader’s name on all the lumber it produces as a sign of quality.
The market for lumber is in a constant state of flux based on factors like the time of year and current customer demand, and mills like Pleasant River Lumber need to be highly efficient to stay competitive—and this efficiency needs to begin almost immediately after a tree is cut.
In Pleasant River Lumber’s original approach to lumber processing, tree-length logs—up to 64-ft long, the most economical for a mill to purchase—were delivered to the mill yard where five manual “slashers,” large circular saws, cut them into 16-ft lengths, usually leaving a short piece as waste.
“Since the entire process was done manually on multiple logs at the same time, there was no optimization of the material or of the time and effort required to process it,” said Christopher Brochu, one of the six partners who operate Pleasant River Lumber. “A human being made a decision as to where to cut each log, and it was impossible to determine accurately how to cut the log to get the greatest value from the material,” Brochu said. In addition, operating the “slashers” themselves was expensive in fuel and labor, and the company lost money on the waste material, which often had to be trucked away.
Getting an optimum Look
When Pleasant River Lumber purchased its Dover-Foxcroft, Maine, mill in 2004, the partners committed to a $12 million investment to modernize the facility, including the part that processed tree-length logs for milling. Recognizing the benefit of leveraging technology for improved productivity and efficiency, the partners turned to Maine-based Progress Engineering, which specializes in designing and implementing process automation solutions, with forest products industry experience. Progress Engineering designed a hybrid system using solutions from a number of vendors, which would allow Pleasant River Lumber to increase efficiency by getting the greatest amount of fiber possible from each tree-length log.
As Dana Hodgkin, the president of Progress Engineering, explained, the new process begins in the mill yard where each individual log is evaluated using a vision system that captures images of the log. Six ceiling-mounted color cameras work in tandem to take images of each log. These images are “stitched together” by a vision appliance and vision system software, which “calculates the length and diameter of each log, with accuracy to within an inch,” Hodgkin said. “That data is then seamlessly communicated via Ethernet with a PLC optimization system developed by Progress Engineering.”
Progress Engineering’s original design used a camera from another manufacturer, and Hodgkin cited problems with this design from the start. “The first camera we considered…didn’t offer a way to capture a clear view of an entire log, which was critical to getting the accurate measurements that ensured the rest of the system operated as required. There were also challenges with the other camera’s ability to operate in a rugged mill environment,” he said. “When our first design failed, we researched alternatives.”
Since the competitive solution had challenges operating effectively in an environment where conditions, particularly lighting, changed frequently, ensuring the new vision system could work under these conditions was a key selection factor. One wall of the facility is open to the elements, which means that lighting, temperature, and even wind can vary from hour to hour. The vision system used offers automatic ambient light detection and can change the exposure time quickly to provide the right level of contrast between the log and the background for each image.
LED lighting was applied overhead for greater consistency. The vision system adapted perfectly to the changing conditions, Hodgkin said, who also praised the machine vision experts involved.
Once the PLC system receives the data about the length and diameter of each log, it integrates with a new “bucking system”—equipment including log singulators and saws—that forms the majority of the new production system. Manufactured by Endurance Equipment, this part of the system analyzes the data from the vision system, determines the optimum location for each cut, and then cuts each tree-length log in a process that is fully automated.
“Investing in this new system was critical for Pleasant River Lumber to become more efficient, and to be highly efficient, we need to get the most usable material possible from each log,” Christopher Brochu said. “Raw material accounts for 70% of our total cost, so the more lumber each log generates, the more competitive we can be.” The new vision system begins the production process with “precise measurements of each log.”
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Right view benefits
Since the new system was implemented, the change has been so significant that Pleasant River Lumber’s partners see few similarities between the new production process and the previous approach. In particular, they note that the vision system has helped them meet several of their key objectives, beginning with determining the accurate length and diameter of each tree. “The critical starting measurement…enables the rest of the system to calculate exactly how a log should be cut,” said Pleasant River partner Jason Brochu. “Getting an accurate length and width measurement is vital because the saws on the new system are accurate to a quarter of an inch, but this is irrelevant if our initial measurements aren’t right.”
Another of the company’s key objectives was to speed processing time, and the new system increased production capacity. The vision system can calculate the measurements of each tree-length log in about 7 seconds, or evaluate about 9 logs per minute.
“This is nearly 10 times faster—and far more accurate—than our previous process,” Jason Brochu added. “While this is a highly automated process, an operator is still involved for the brief second required to assure that the decision the system makes is accurate. There is an override capability if needed, if a log has a significant defect, for example, but since implementation, we’ve found that the system is accurate more than 95% of the time.”
It wasn’t a stated objective of the project, but Pleasant River Lumber is committed to ensuring the health and sustainability of Maine’s forests, and the new system supports this mission by virtually eliminating waste. “All lumber processing is now done at a central location, so we can capture everything from the small pieces that can’t be used in production lumber to the sawdust and bark,” Christopher Brochu noted. “Then we can sell it all at a profit to get value for every by-product of the system. We now have a zero-waste operation, which aligns with our environmental goals, and gives us a new revenue stream.”
Dimensions match market
Lumber is a “commodity,” so the product itself has little to differentiate it from competitive solutions. Pleasant River Lumber’s new automated system gives the company competitive differentiation in the marketplace, however, in that the dimensions of the lumber produced can be changed quickly to meet market conditions. For example, if certain lengths and dimensions are in greater demand—and so are selling at a better price—Pleasant River Lumber can cut its logs accordingly, meeting the demand sooner.
“Our new production system has made us more efficient, more productive, and more nimble,” said Jason Brochu. “Because we can work quickly and accurately, we have the flexibility needed to change the lengths as often as we need to, to adjust to the current market. With our old system, changing the length of the logs we cut was virtually impossible,” Brochu said.
The newly integrated vision system “is a key element in a new lumber production system that has completely transformed the way Pleasant River Lumber does business,” Christopher Brochu concluded.
– Maureen Clancy is marketing project manager at Teledyne Dalsa. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, firstname.lastname@example.org.
Progress Engineering www.progresseng.com
- Integrated vision system speeds production, maximizes efficiency at sawmill
- Tree-length log measurements are calculated in about 7 seconds, 9 logs per minute, nearly 10 times faster than previously.
How much faster would your throughput be with faster measurements?