Cut waste, downtime: More exact position sensing

-- Control Engineering, 2/5/2008

Clawson, MI, and Newton, NC — Improved operational efficiency and reduced scrap were the result of high technology position sensors at a Michigan manufacturer. Learn about the sensing technology and application.

Gemco 953 Series Vmax from Ametek Automation & Process Technologies (APT) has improved operating efficiency at Gregory Wood Products, a manufacturer of dimensional lumber. Wood scrap was also reduced by replacing linear displacement transducers (LDTs) in the company’s wood machining operation.

A laser-guided edger at Gregory's North Carolina factory profiles each log, determines the optimum cut, and machines the rough log into usable boards. LDTs installed on hydraulic cylinders position and guide the edger, which averages a cut board every three to five seconds. A wrong cut immediately results in a scrap board. Severe shock and vibration are an inherent part of the operation as the edger's hydraulic cylinders extend every three to five seconds up to 18 in. from home position as dictated by the laser profile. Gregory had experienced high failure rates for its LDTs and excessive wood scrap until it replaced its LDTs. Since incorporating the Gemco 953, Gregory has not experienced a fault due to an LDT failure.

"The prior LDT units were continually generating faults (losing position)," said 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 the severe shock and vibration. This is by far our most extreme application, which Gemco has performed with ease." Company vice president, Steve Randall, added, “We significantly reduced maintenance time and wood scrap, which had averaged $3,000 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."

Gemco LDTs, which feature magnetostrictive position-sensing technology, are known for their performance in extreme environmental conditions, Gemco says. The LDTs are used in steel mills, primary and secondary metals processing, rubber and plastic injection-molding, extrusion equipment, and material handling machinery. The sensor is shock resistant to 1,000 G, vibration-resistant to 30 G, and is IP68-rated. The digital LDT offers reliable absolute position indication with high resolution and precision repeatability and overcomes the resolution and signal limitations of analog LDTs by offering infinite resolution and a stable position feedback for cable runs up to 1,200 ft from the host controller. Gemco 953A (analog) and 953D (digital) VMAX LDT offer active measuring range of up to 300 in. and wide power supply voltages ranging from 7 to 30 V dc.

For related reading from Control Engineering:
Product Research: Position Sensors

Cover story: Sensors: Getting into Position

— Control Engineering News Desk
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