Replacing Dancers With Load Cell Feedback Tension Control

It’s not always necessary to buy a new machine to get high performance. Sometimes re-engineering an existing production line with state-of-the-art web guides, drives, tension controls and other modern features delivers the best ROI.

Tension control is a key factor in Arkwright’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 Dover Flexo Electronics’ Tension Roll® transducer. 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 attention.”

SteadyWeb 6^TM Automatic Tension Controller

DFE’s Tension Roll® transducer is actually an integrated dead-shaft idler roll and two load cells 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, “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.

Tension Roll® Transducers

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 fitment of cartridge load cells and a separate idler roll. The Tension Roll® is sized to fit the exact width of the machine frame.

“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 nearly 50 Tension Rolls® installed at its plant over the last 10 years, Arkwright has only had to repair four. The Tension Roll® is competitively priced with other tension control systems that use a roller and two load cells, says Markel.

Typical dancer control retrofits incorporate:
• A closed-loop tension controller such as the SteadyWeb™ 6
• A load cell such as the Tension Roll® Transducer
• A pneumatic brake, electric brake, clutch or motor drive system

Customers integrating tension control with a PLC most often utilize:
• A load cell signal amplifier such as the TA1 TrueTension™ Amplifier
• A load cell such as the Tension Roll® Transducer, a pair of convertible load cells such as the Model C Series Transducers or Under Pillow Block Transducers such as the Model F Series