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Lou Kren
Senior Editor

Trends in Coil Feeding

January 1, 2018

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...include power uncoiling for tougher, thicker material; flexibility to handle higher- and lower-gauge product; and more.

The centerpiece of any press line, the press itself, gets all the press, so to speak. Most of us probably are familiar with stamping-machine technology advancements and the advantages they bring, from the introduction of servo-driven units to the use of simulation to construct more robust presses to controls advances that allow for flexibility in speed, line integration and process-monitoring functions. But it all starts with the feed. Material must enter the press straight and true, and in synch with every other line component. If not, be prepared for scrap, lower quality and increased downtime, and their negative impacts on the bottom line.

To be sure, coil feeding has evolved to deal with newer breeds of material, and the increasing needs of metalformers and their customers. To take stock of the evolution, MetalForming spoke with David Hui, senior manager-controls engineering for Colt Automation (www.coltauto.com), Mississauga, Ontario, Canada.

Built to Feed Stronger Material

Robust material demands robust equipment and new ways to route it through the press. To handle heavy-gauge material, a power uncoiler with tension control, reinforced straightener and beefed up rolls, and a servo feeder with holding brake are must-have configurations.

“A 15-30-hp uncoiler motor, for example, often is specified for uncoiling such material,” Hui says. “It has the power to keep the coil tight to ensure proper material feed. Unwinding force is so high when feeding heavy-gauge material that the coil can unwind by itself if the tension is too low, and the straightener can be damaged if not engineered properly. The regenerative power of the uncoiler will feed back to straightener through a shared DC bus, instead of dissipated on a dynamic-braking resistor.”

Absolute encoders accurately track rolls, guides and pass-line positions, and information in job recipes enable monitoring and control of position and other variables to keep machinery operating efficiently and effectively.

Do not, Hui stresses, attempt to run higher-gauge material on feed equipment not rated for such use. For example, the tension created via an uncoiler with an air brake does not even approach the tension created by a 5-hp motor.

A press line starts with the uncoiler. For tougher, thicker materials, a motor may be installed to assist with uncoiling. Powered uncoilers deliver synchronization with other press-line components, thus providing material feed at proper speeds without undue stress on feed-line components.

“Such equipment cannot accurately hold this material,” explains Hui, “and trying to do so will increase scrap production, damage equipment and lead to expensive downtime.”

Whereas feed equipment once could only handle higher- or lower-gauge material, on the scene today are systems that can feed both. Hui notes Colt-installed feed equipment that can adjust to material gauge ranges through the flick of a switch, which reconfigures the machinery. For heavy-gauge material, the uncoiler operates in tension mode and material is pulled off from the mandrel by pinch roll, while for light-gauge material, the uncoiler, in speed-control mode, offers less tension and the pinch roll is bypassed.

Improved Line Integration

“Better integration increases productivity.”

With those words, Hui details how integration has improved and what it means for metalformers.

“An operator may have to enter job information on numerous consoles, perhaps separately for the press, a transfer system and the feeder,” he explains. “Back and forth, back and forth. That wastes time. By working with press manufacturers, feed-equipment providers such as Colt Automation have been able to integrate feed controls into job storage on the press control. Punching in a job or part number automatically sets all feed parameters, including pass-line height, progression speed, acceleration, loop settings, etc.”

The use of electronic-cam motion profiles to replace mechanical cams represent another advancement in line integration.

“Now, the feeder actually cams to the press, similar to a mechanical cam but without mechanical linkages,” says Hui. “Speed and acceleration follow the press. This makes a lot of sense when attached to a servo press, which allows the feeder to run at 350 strokes/min. or whatever speed at which the press is running.”

This allows feed equipment to properly synch to the unique speed variations of servo presses. With high-speed communication (Siemens Profinet RT, for example) the press can share its master axis with the feeder and/or transfer line, ensuring synchronicity all the way through the press line.

“So everything is cammed to the press, with every other line component following the press as a slave,” Hui explains.