Q&A: Collecting Process Tension Data Over Time

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DFE 30th Anniversary

Tension control is a key factor in Arkwright Inc.’s efforts to enhance its overall process control and attain repeatable numbers, says Glenn Markel, director of engineering. Based in Fiskeville, RI, the specialty paper and film coater has gradually replaced its more traditional dancer tension and pneumatic controls with the Dover Flexo Electronics Tension Roll^Ò . Other Dover Flexo products have been integrated into its lines as well, such as indicators and brakes to enhance performance.
"Dancer controls were a constant maintenance problem," says Markel. They’re delicately balanced and have a lot of precise components, so they require constant tension monitoring."

The Tension Roll is actually an integrated dead-shaft idler roll and two tension transducers combined into one unit that measures tension and supplies a signal via an automatic tension controller to Control Techniques digital drives. A very accurate method of controlling speed changes, it [the DFE tension control system] doesn’t require the dampening a dancer system does, says Markel.

"If you have a sudden shock in the web, a dancer ‘dances’ to compensate, and it is a kind of touchy-feely process to dampen it out," he says. "But with the Tension Roll, speed and tension are so accurate and track so well, shocks and surges in the web are not the problem they used to be."

Unlike traditional tension measurement systems that use an individual, discrete transducer and cable connected to each end of an idler roll, the Tension Roll has a single cable at one end. This eliminates the problem of a second cable, which typically has to cross over the coater to link the transducer to the control electronics at machine side.

The Tension Roll also eliminates extra design time spent installing load cells or traditional tension transducers into the web path. The plant engineer doesn’t have to resize the width of the machine frame or devise complicated mounting configurations that are required to accommodate load cell/ transducers and a separate idler roll. The Tension Roll is sized to fit the machine frame exactly.

"All you do is drop them in place, align and calibrate them," says Markel. "And they’re practically bullet proof because they’re self contained without a lot of extremities."

Of the approximately 50 Tension Rolls installed at its plant over the last 10 years, [Arkwright] has only had to replace four. The Tension Roll is competitively priced (approximately $1,400/roll) with other tension control systems that use a roller and two load cells, says Markel.

This article was excerpted directly from its complete version in the April 1998 issue of Converting Magazine. It was written by Stephanie Duschene, Senior Editor.