For decades, sawmills turned out lumber the old-fashioned way, leaving valuable trimmings -- literally -- on the cutting-room floor. But in recent years, automation has proved the key to improved sawmill efficiency and profitability.

At the Langdale Forest Products Co. sawmill, old-world cutting has met hi-tech automation in the form of a state-of-the-art sawmill control system from Rockwell Automation. Langdale, based in Valdosta, GA, has increased its lumber production by 35% and dramatically reduced the amount of wood that goes to waste. Its newly installed Allen-Bradley control system routes logs through a highly automated sequence of debarking, trimming, cutting, planning, and bundling processes, leaving the finished product -- lumber -- ready for shipping. Their experience shows how a manufacturing facility can increase its productivity without increasing its labor costs or the amount of raw material it uses.

A Leader in Southern Yellow Pine Production

Langdale has been producing construction lumber on its 200-acre Valdosta sawmill site for more than 50 years. Roughly 30% of the felled trees that arrive for processing are harvested from Langdale's vast yellow pine forests throughout the South and then hauled to the sawmill, which receives more than 100 truckloads of felled trees daily. These truckloads of logs, once they're processed, may be shipped as far away as the Caribbean.

Production Challenges

Reducing a log to lumber, though it appears simple, is fraught with potential difficulties. Heavy logs and lumber move through the sawmill quickly, and production uptime and operator safety are prime concerns to management and plant floor employees alike. The original Valdosta sawmill's recovery rate -- the amount of salable lumber extracted from a log -- was too low for the company's desired profit margin. Another negative result of low recovery is that it requires too many trees to be harvested in relation to the amount of lumber produced. The original sawmill was simply not recovering enough lumber, and it required many personnel on the floor, leading to increased labor costs and a higher possibility of accidents.

Ever conscious of production and profitability goals, Langdale's management decided in 1998 to build a new sawmill -- complete with state-of-the-art automated controls, cutting equipment, and buildings. John Lindsey, Langdale's electrical manager, needed to solve two main problems: increase the sawmill's recovery rate, and maintain or even bolster the company's reputation for producing a superior product. In doing so, Langdale's management sought to implement a plantwide integrated control system with the following attributes:

• A state-of-the-art control system to meet Langdale's production requirements and allow for increases in production rates or plant expansion, as well as capture information to enhance plant management and operation


• A highly automated log assessment system that would quickly and accurately determine how to cut each log for maximum recovery


• A production system that would substantially enhance the safety of sawmill floor personnel


• The ability to produce a finished commodity that met Langdale's strict quality standards.

Since the aging Valdosta sawmill operation had been controlled by Allen-Bradley equipment, Lindsey called on Valdosta-based Allen-Bradley distributor Steve Shiver, from Englewood Electrical Supply, to lend his expertise. "We had been working with Steve and Rockwell Automation for some time," Lindsey said. "And after looking at other offerings, we saw no reason to change that. We've always been well-supported by Steve, so we went right to Rockwell Automation."

Personnel from Langdale and Englewood designed a complete sawmill operation -- from debarking to board identification stamping -- based on Rockwell Automation technology. The installed system includes 20 Allen-Bradley PLC-5® controllers and five Allen-Bradley SoftLogix(TM) soft controllers, a Rockwell Software RSSql(TM) transaction manager and RSView32(TM) human machine interface (HMI) software. Though primarily programmed in ladder logic, Lindsey also programmed some system components in-house when he needed to enhance the ability of ladder logic to work with some of the special equipment Langdale operates. A common programming tool allows engineers to easily instruct a wide variety of components.

Management decided on a mix of hard and soft control, based on each section of the sawmill's requirements. With some of Langdale's cutting applications requiring custom-programmed control in the C programming language, it made the most sense to use SoftLogix, which allows for custom, C-based programming and is particularly well suited for Ethernet communications within the facility. Other applications requiring more standard control instructions use the robust PLC-5 controllers. Both hard and soft controllers use RSLogix(TM) as the configuration environment and a common set of supported networks.

Not a Scrap Wasted

Log-to-lumber processing is fast and complicated. But in the newly automated Valdosta sawmill, a plantwide integrated control system holds the key to an efficient lumber production process. After a crane operator moves a 2-ton log onto the processing line, the lumber-production process begins. First, the log runs through a de-barker, which chews off most of the bark. From there, the conveyer system, which routes logs and lumber throughout the entire production process, pulls the log through an optical scanner. The scanner measures the dimensions of the log and a SoftLogix controller instantly determines how the log should be cut for further processing down the line. Saws then cut off each of the log's rough ends and the conveyer moves it horizontally through a step feeder and log ladder to the canter/quad system.

On its way to the canter/quad system, which removes a parallel pair of a log's edges, the log runs through a metal detector to detect any metal pieces that may be embedded in the wood. Another scanner sends information to a second SoftLogix controller, which determines how best to position the log to cut off an opposite pair of its edges, lengthwise. Following the controller's instructions, a machine rotates the log into optimum position before pushing the log through the canter saw.

The log emerges with two flat and two rounded sides, which may still sport a thin layer of bark. (The rounded edges that have been trimmed move to another part of the line for further processing.) The conveyer aligns the log for yet another scanner, which feeds its data to a SoftLogix controller that instantly determines how the log will be cut into boards. This information is sent to an Allen-Bradley PLC-5/60E controller, which, in turn, controls the curve saw gang.

The curve saw gang has twelve parallel saw blades that the controllers can adjust to extract the maximum amount of lumber from a particular log. For example, if a log is to be cut into three 2 in. by 4 in. boards and one 1 in. by 4 in. board, the controllers will automatically set the gaps between the saw blades to make the appropriate cuts. In addition, the controllers can instruct the blades to move laterally as a group to conform to any curvature in the log, thereby producing straight boards.

After the sawmill process has cut the log into varying sizes of raw boards, two plant personnel quickly weed out any defective boards. Then a scanner scans the remainder for size as they move further along the line. The scanner sends the size information to the sorting machine, which automatically sorts and puts the wood into bins, after which it's stacked for drying. After boxcar-size steam-fired dry kilns dry the boards for up to 24-hours -- depending on the raw lumber's moisture content -- the dried boards cool outdoors, weather permitting.

Next, a forklift delivers the dried-lumber pallets to the final processing and finishing building. A conveyor moves the lumber to a high-speed planer, which sheers 1/8 in. from each board's four longitudinal faces in a half-second. From the back of the planer, boards shoot out in quick succession and slowly align horizontally for the grading personnel. Here the finished product receives the most human contact.

As the lumber files past, the graders manually examine and assess each board according to its trueness, absence of knots, and other attributes, and mark each board with a special marker. Down the line, a sensor reads the marker's special ink, triggering a stamping machine to print the appropriate identification label onto each board as it moves into the sorter.

Once planed, graded, and labeled, the lumber has ended its production run. The boards are then sorted by type of board, bundled, and strapped into stacks. Finally, forklifts cart the stacks of finished lumber either to a truck or a temporary storage area.

Throughout the entire plant, Lindsey established production processes and programmed the newly installed Allen-Bradley controllers to cut and trim every piece of usable wood into salable lumber. Beyond that, every scrap and chip of wood eventually finds its way into a product. Personnel sweep wood chips from the plant floor and lumber yard, and the company sells them and other wood scraps to nearby plants that turn the chips into fiberboard. Langdale even recovers the sawdust and fuels its drying kilns with it. Absolutely nothing goes to waste -- even chips and dust swept from the grounds enter the product stream. Thus Langdale's sawmill is a fiscal success, and has a sure goal for any production facility: zero waste.

The various control modules of the sawmill automation system are linked via an Ethernet network. Each production process has its own "identity," and can be viewed as a complete subsystem. The use of Ethernet for information sharing allows Langdale easy integration with plantwide computer systems.

For example, the curve saw gang subsystem (mainly responsible for increasing recovery rate from the timber) essentially runs independently from the rest of the sawmill. A scanner scans the logs, and a SoftLogix controller interprets the log attributes, and sends the rotation, curve, and cutting information to an Allen-Bradley PLC 5/40E. The controller then sends cutting and movement instructions to the curve saw gang and its log-positioning system via hardwire. This scenario is typical throughout all the sawmill's discrete processes.

To tie the curve saw gang from the controller systems to the management-level Microsoft Access® database, the Valdosta mill installed the RSI RSSql transaction manager. RSSql runs on Ethernet and writes production data to the database, allowing floor personnel and management to view operations from any RSView32 HMI station in the sawmill or from the mill's main office across the street.

"Easily retrieving production information allows us to track production trends and match them to demand and price trends," said Jim Langdale, vice president and general manager. "It's a valuable tool for making sure we don't have any shortfalls or too much overstock."

Model of Efficiency

Thanks to Rockwell Automation and its Allen-Bradley control system and the hard work of Lindsey and Shiver, the new Valdosta plant has been able to increase productivity with its existing plant personnel. Production is up an average of 35% over the old sawmill's average -- 15% higher than the old plant's best year. "This is because we're recovering more lumber from the logs, not because we're processing that many more trees," Lindsey said.

Langdale employees especially appreciate the new plant's efficiencies. "When the new plant began operation," Langdale said, "we not only increased production, we increased employee wages and benefits by 20%."

SoftLogix, RSSql, and RSView32, and RSLogix are trademarks of Rockwell Automation. PLC is a registered trademark of Rockwell Automation. Microsoft Access is a registered trademark of the Microsoft Corporation.