New Gear Equipment Sawmilling
Sonic Grading

The Simpson Lumber Company is one of the most established lumber producers in the Pacific Northwest, and has been in business since 1890. In March of 2015, the company sold its Tacoma-based sawmill, the Commencement Bay mill, along with three other sawmills, to Interfor Corporation at a cost of $94.7 million plus additional working capital and future contingent payments.

Simpson Lumber’s rich history has come as a result of wise decision-making by the staff in terms of key investments for the mill that will benefit the company long-term.

Greg McCoy, dry end superintendent at Interfor’s Tacoma Division, knew that machine stress rated (MSR) lumber could be an important product for the mill.

“Once we decided to use acoustic technology to produce MSR, we chose Metriguard,” he says. “They have long been the industry leader and specialize in MSR.”

McCoy has a long history in the MSR industry. In fact, one of the first Metriguard MSR installations was at a Simpson Lumber mill in the 1970s. The Model 2350 SLG is a result of four decades of experience in acoustics and lumber grading equipment.  

Metriguard installed a Model 2350 Sonic Lumber Grader (SLG) at Interfor – Tacoma Division. The mill, located just a few hours drive south of Vancouver, produces Douglas fir and hemlock dimensional lumber for use in the home construction industry.

The Model 2350 SLG is a transverse flow grader that uses proprietary scales to compensate for off-axis loading, improving accuracy and repeatability in the weight measurement.

“This transverse method of producing MSR is ideal for mills that have limited space for installation,” says Dan Uskoski, vice-president of sales for Metriguard. “The density-only component of this equipment can be an important tool in sawmills to help make lumber resource allocation decisions before drying.

A rugged electro-mechanical hammer, requiring no shop air, strikes the end of each piece of lumber. The resulting acoustic signal is analyzed by software developed and maintained in-house by Metriguard engineers. Piece density and acoustic signal are used to determine the modulus of elasticity (E). In the mill, data is handed off to an optical scanner for final MSR grade determination. Remote access capability allows for troubleshooting issues as they arise. 

Metriguard engineers have developed and will continue to maintain and improve the operating control and data processing for the system. Piece measurement data and acoustic signal information are used to determine a modulus of elasticity (E) for each piece.

“Preparation for installation of the system requires a structural steel beam under the lug chain for mounting the scales,” Uskoski explains. “Piece measurement sensors are attached to surrounding structures. A cut is made in the lumber line fence for the hammer and microphone assembly and the unit is mounted to the floor or mezzanine. The electronics cabinet and operator interface are mounted near the hammer assembly.”

 McCoy values Metriguard’s input and candor regarding equipment capabilities and has found them to be above-board and honest. He has been impressed with Metriguard’s efforts to ensure proper operation of the system. In short, he knew that Metriguard would “make it right.”

“I can’t say enough about how the guys have responded to questions, issues and concerns. I would definitely recommend Metriguard to others,”  McCoy concludes.

Several challenges may be encountered during a Model 2350 SLG installation, according to Uskoski.

“Running conduit to connect all of the system components to the control system requires working around existing electrical and hydraulic systems,” he says. “In addition, integration of the data handling with other systems involves coordination with both the mill personnel and other vendors. Follow-up issues after the initial installation can be addressed via remote access, allowing Metriguard personnel to make software adjustments as needed.”

The result is the right solution that the team at Interfor needed for the efficient production of MSR for its customers.