A recent upgrade at a southern yellow pine mill in Alabama has had a major impact on the mill’s productivity with the addition of profiling incorporated into the mill’s curve sawing gang process. The mill was facing daily bottlenecks at the edger that resulted in backed up lumber decks, hours of overtime work to clear the backlog, and continual maintenance to keep the overworked components operating. Today lumber is flowing, and the bottleneck has moved on down the line to the kilns. And there is a solution in the works to ease that pain as well.
The Canfor southern pine mill at Fulton, Alabama started producing southern yellow pine dimensional lumber as Scotch Lumber Company, a family-owned operation in the late 1800s. After a brief closure in 2009 due to economic conditions, it merged with Gulf Lumber and reopened as Scotch Gulf Lumber in 2010. Then in 2013 the company entered a phased purchase agreement with Canfor Corporation, with the sale complete by 2016.
“I believe our mill was a perfect fit for Canfor,” said Perry Callaway, plant manager. “They saw the potential in the mill, its equipment and people, its strong timber base and its product mix.”
The mill employs 147 people, and features dual log processing lines, one for small logs up to 27″ in diameter and one for large logs up to 46″. It produces dimensional lumber products from 2×4 to 2×12, MSR (machine stress rated) lumber, #1 and #2 prime lumber, and specialty grades. The mill also produces 1×4 and 1×6 boards that are shipped green (undried).
Holding Up the Line
An ongoing bottleneck at the board edger was a major slowdown in the productivity of the entire operation. The original configuration of the mill had boards exiting the gang and being transported directly to the trimmer. A significant amount of the lumber was being tippled out after the trimmer, and routed to the edger for remanufacture.
“The edger was doing all it could but was just overwhelmed with reman lumber,” said Perry. “We would start processing logs at 6:00 am and by 9:30 we’d have to shut down the headrig and canter/ bandmill because all the lumber transfer chains would be blocked up,” continued Perry.
Adding to the productivity issues, there were also safety concerns as the lumber was crossing up on the decks and required manual straightening. The plant’s edger, trimmer and stacker operators were often required to work until 8 o’clock at night just to catch up so the mill would be ready to start up the next morning. There was also the issue of maintenance personnel constantly working on the tipples behind the trimmer.
“Our reman was typically 13-14%, or 6,000 to 7,000 pieces per shift,” said Perry. “We were literally beating our tipples to death with so much reman lumber.”
Plant management felt that the potential productivity increases and cost reductions that the mill could achieve would be significant if they could keep the line moving forward.
A History of Achievements
The Canfor plant had employed equipment from USNR to upgrade its lines through the years, so it was natural for mill management to canvass USNR for a solution to the bottleneck dilemma. George Krumbine, USNR account manager, worked with the Fulton team to determine the best configuration that would improve the mill flow and increase productivity and recovery. The project team recommended retrofitting the existing curve sawing gang with a new shape chipping canter and a shape chipping profiler, as well as improved scanning and optimization.
“We considered other vendors’ solutions, but one of the main reasons we decided to go with USNR was the mechanical simplicity of the USNR approach,” said Perry. “It was pretty much what all the millwrights were used to working on every day.”
How It Works
The new solution incorporates a chipping canter and profiler ahead of the saw box. The shape chipper skews and slews as it chips off the cant’s sides via conical chip heads. Then, the four-sided cant is fed through the shape profiler eliminating much of the requirement for edging the boards. Not only does profiling reduce the need for edging, it also smooths much of the flow which vastly improves productivity. For profiling, the existing horizontal saw box cuts the cant into boards.
The project included new scanning and optimization, as well as controls for the line. The original scanning was performed with a single lineal scan zone, as there was ample time to pass the solution on to the gang’s control system before the cant entered the machinery. Also, the original system did not require optimization for shape chipping and profiling.
The new configuration includes three scanners along the scan belt. This allows the system to complete a full scan of the cant in only nine feet of travel, and allows time for the optimized solution to reach the programable logic controls (PLC) and set the cutting tools to implement the decision. The cants are fed horizontally onto a rollcase from both sides, coming from the large and smaller log lines. They are fed onto a scan belt where they are transported lineally through the three scan zones and to the shape chipper’s infeed. The shape chipper infeed controls the cant with three powered top press rolls that secure the cant on the chains while feeding it through the conical chip heads.
The profiler infeed has two powered top press rolls to secure the cant, and two reference rolls that feedback the cant’s position to the PLC system. This allows the PLC to control the skew and slew of the profilers to carry out the optimized profile solution. Reference rolls are also included on the gang’s existing chipper arbors (just upstream of the saw box) to allow the PLC to set the saws relative to the chipped surfaces of the cant. The gang infeed employs three powered top press rolls and a bottom feed roll to secure the cant while it is transported through the double arbor saw box. While the new components included the latest controls technology, the existing required PLC updates.
A Team Approach
The project team was led by Jack Few, Canfor project manager, and Kelly MacDonald, his counterpart on the USNR side. Daily meetings kept everyone updated on progress and resolved any issues as they arose. Key among the group’s priorities were adhering to an aggressive schedule and maintaining a safe working environment.“
Safety was our first priority on this job as we had about 80 people working on site,” said Perry. “When the job was complete we had never needed as much as a single band-aid. The men and women at USNR are very courteous and professional in every aspect of their job. And after the project was complete, USNR has always been ready to help when we needed technical support.”
Increased Productivity Now, Plans for Future Upgrades
“The new system has exceeded all our expectations,” continued Perry. “When we started the project, we were really hoping our production would increase to 60,000 board feet per hour, but we’ve blown past that goal. As of now we’re right around 62,000 feet per hour, and all the operators are happy that fifteen minutes after the mill goes down at the end of a shift, all the lumber is caught up and they get to go home.”
Based on the success of the recent mill upgrades, the Canfor team is talking about what improvements they can make next.
“We have a target of about 130 million board feet of production this year, but we have plans to increase our output beyond that level once we complete other upgrades throughout the plant,” concluded Perry. “With that goal in mind, we’ve already ordered a new USNR continuous dry kiln, and we plan to have it up and running by the first quarter of 2018.”