LDT Cuts Waste and Downtime in Lumber Processing

Dimensional lumber is a commodity product, so it must be produced rapidly with tight dimensional tolerances. Gregory Wood Products, Newton, N.C., a leading manufacturer of dimensional lumber, has been able to walk this tightrope by significantly improving operating efficiency and reducing wood scrap. One way it’s done this is by replacing linear displacement transducers (LDTs) in its wood machining operation with Gemco 953 Series Vmax transducers from Ametek Automation Process Technologies, Clawson, Mich.

Gregory wood Products improved machine reliability by providing magnetostrictive LDTs with high (1000 G) shock and 30 G vibration tolerance.

A key to Gregory’s operation is accuracy. A laser-guided edger at Gregory’s factory profiles each log, determines the optimum cut, then machines rough-cut logs into usable boards. LDTs installed on hydraulic cylinders accurately position and guide the edger, which averages a cut board every 3 to 5 sec. A wrong cut results in a scrap board. Severe shock and vibration are inherent to the operation as the edger’s hydraulic cylinders extend up to 18 in. every 3 to 5 sec as dictated by the laser profile.

“The prior LDT units were continually generating faults (losing position),” notes Cecil Gregory, co-owner of Gregory Wood Products. “Although the exact reason for the failures is still unknown, we strongly speculated that it was caused by severe shock and vibration. This is, by far, our most extreme application, but the Gemco sensors have performed with ease.”

A successful solution

Gregory experienced both high failure rates for its LDTs and excessive wood scrap until it replaced them with the Gemco 953 Series Vmax last year. Since incorporating the Gemco 953, Gregory has not experienced a single fault due to an LDT failure. The previous LDTs had faults as often as every 15 minutes on some days.

“We significantly reduced maintenance time and wood scrap, which had averaged $3000 per day due to LDT failures. In addition, we were able to install the 953 Series in minutes into the existing LDT footprint on our equipment. With the success of the Gemco 953s in our cutting operation, we now plan to install them on the wood stackers and sharp chain as well,” comments Steve Randall, vice president of Gregory Wood Products.

Gemco LDTs rely on magnetostrictive position-sensing technology, and many configurations are available to meet specific requirements. In addition to lumber and forest products equipment, Gemco LDTs have found application in steel mills, rubber and plastic injection-molding, extrusion equipment, material handling machinery, and primary and secondary metals processing — such as stamping, roll forming, and die-casting.

Vital statistics

The 953D Vmax is well suited to applications that undergo shock, vibration, extreme temperatures, and exposure to contaminants. It is shock resistant to 1000 G, vibrationresistant to 30 G and is IP-68 rated. As is typical with magnetostrictive LDTs, the fully digital 953D Vmax offers accurate and reliable absolute position indication with high resolution and precision repeatability. It overcomes the resolution and signal limitations of analog LDTs by offering infinite resolution and a stable position feedback for cable lengths to 1200 ft from the host controller. Both the Gemco 953A (analog) and 953D (digital) Vmax LDT offer active measuring range to 300 in., and analog output units offer programmable zero and span.

Both units feature visual and output signal diagnostic feedback and standard cord sets for maximum value. A tri-color LED indicator verifies proper operation and distinct diagnostics for quick troubleshooting. Their low power consumption (1 watt typical) allows direct connection to displays and control interface modules.

For more information, call Ametek Automation Process Technologies at (800) 635-0289, visit www.ametekapt.com.