Advanced controls help crosscut saw provide high precision and high throughput
Since 1996, Portland, Oregon-based Pacific Trail Manufacturing, Inc. has innovated to produce a range of crosscut saws that process full units of lumber, plywood and other wood types to length quickly and to tolerances as precise as 1/64th of an inch (0.4 mm). Their powerful, industrial chainsaws are used around the world by lumber remanufacturers, truss manufacturers and pallet makers, even at a wood products depot in largely forest-free Kuwait.
“Any company using high volumes of cut-to-length wood products can benefit from our specialized saws,” says President Tom Langton. “They produce consistently precise cuts despite variability in the wood feedstock, which can be dry or wet. If it’s the latter, a palette of feedstock can weigh up to 20,000 pounds, but our saws can still position and cut to our customers’ precise requirements.”
Despite its success, the company has remained purposefully small. Its staff is just 10 people. Langton handles sales, and co-owner Bruce Wold manages engineering, installations and service. This small staff recently upgraded the company’s most sophisticated cross- cut saw, the Accu-Cut.
That saw operates with the automated precision of a CNC (computer numerical control) machine. Most customers average between 80 and 100 cuts a day, programming up to 20 different recipes, each with 10 different cuts. One of the Accu-Cut’s hallmarks is a gear-and-bar conveyance system that precisely holds and positions tons of milled lumber for precise cuts.
“What might take three workers 45 minutes with other saws takes just one worker 10 minutes with ours. With a unit saw, you can create 200-plus 92-5/8” studs in under two minutes,” Wold explains. “But if the cutting tolerance isn’t consistent in holding 92-5/8”, you’ve quickly created a finished product that you can’t use.”
The Accu-Cut has fewer wearable parts, so customers experience little or no downtime. That’s important because downtime isn’t an option for saws needed for production. The Accu-Cut saw’s controls were designed by Charter Controls, Inc., a Siemens Solution Partner based in Vancouver, Washington.
“The saw has a chain-driven carriage system,” explains Victor Gonzalez, a controls engineer with Charter. “Because the long chain length is susceptible to stretching and slack, synchronizing the drive with the mechanical system was very challenging – especially when a palette of wet lumber can weigh up to 10 tons.”
Gonzalez and Charter Controls recently came into the spotlight when the Accu-Cut’s control system was due for an upgrade. It was being built with aging third-party PLCs, drives and separately-wired safety relays.
Gonzalez recommended a major upgrade of its Accu-Cut saw’s controls, drives, HMI and supporting components. Charter Controls designed and built an entirely new control system for the machine, driven by a 20-horsepower AC motor.
WESCO Northwest Automation, a Siemens distributor, provided components. Core to the controls is the Siemens SIMATIC S7-1214FC PLC, a compact, high-performance CPU with integrated safety functions.
“Having fail-safe features already in the SIMATIC PLC greatly simplifies the panel’s design, on top of the PLC’s already small size, both of which also saves space,” says Gonzalez. “And by eliminating safety relays, which require a lot of complex wiring, it also makes panel manufacturing much easier.”
Troubleshooting is much easier too. Although the Siemens SIMATIC PLC product families, such as the S7-1200 series, are widely known for their reliability, he prizes the integrated diagnostics that can be remotely tapped if necessary. In the earlier generation, problems like a faulty safety relay often brought production to a lengthy halt.
Now, Charter Controls can dial into the PLC remotely and know exactly which circuit needs attention, saving plenty of time. In addition to the SIMATIC PLC, the full solution from Charter Controls uses a SINAMICS S120 drive to control the accurate and precise positioning of the Accu-Cut saw’s carriage, even under tons of weight, while a compact SINAMICS G120 drive controls the saw bar.
A nine-inch Siemens Comfort Panel HMI display provides a color touchscreen with plenty of space for operator information and controls interaction. The Charter Controls solution team used the Siemens TIA Portal, a common software engineering framework for its Totally Integrated Automation (TIA) portfolio, to program the SIMATIC PLC with the Accu-Cut saw’s many recipes. The saws use Safe Torque Off to stop the motors during emergency stops.
“The TIA Portal reduced our PLC and HMI software programming time by as much as 30 percent, saving us days if not weeks,” Gonzalez says. “The function libraries that come with the TIA Portal along with the programming diagnostics are big time savers. We can also save our own code for reuse, which extends the value of time invested in original software development.”
Precision remains a central focus. Wold points out that while the saw’s specifications state that it can cut to 1/32nd of an inch or 0.8 mm, actual performance can be accurate to half that.
For example, if the motor starts drawing over 15 or 16 amps, the saw can slow down by as much as 50 percent, adjusting the cutting speed automatically to keep the cut precise. For Charter Controls, having Siemens as its “one-stop-shop” simplifies procurement, manufacturing, commissioning, service and support. Gonzalez also values the open standards Siemens uses in designing and engineering those components, which he says helps integration with needed third-party components.
Overall, the Accu-Cut’s new control panel has helped improve the safety and serviceability with the SIMATIC PLC’s integrated safety and remote diagnostics. While the former is critical for the Accu-Cut’s safe operation, the latter is important for both Wold, as first-line support, and Gonzalez, as the escalation point.
“Being able to dial into a customer’s saw wherever it is in the world is a big advantage for us and for our customers,” Wold says, noting that Siemens worldwide presence is also a competitive advantage for Pacific Trail.Have an Inquiry for Siemens about this article? Click Here >>