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Trends in Coil Feeding

By: Louis A. Kren

Monday, January 1, 2018
 

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.

Eased Coil Changeover

Job-recipe-driven feed lines offer the advantage of automatic coil loading.

“Before, centering a coil to a line meant a lot of walking back and forth for the operator,” says Hui. “No more. Now, the coil automatically positions to the center line, and retaining arms or coil keepers, guides, and rolls automatically adjust to the proper position. Automatic positioning and coil tapering save a lot of time. And, during threading, once the stock passes the straightener, the balance of the threading process can be accomplished through the feeder console. Also, a feeder pendant can jog the straightener. No excess travel by the operator is necessary. Equipment providers such as Colt Automation have been trying to minimize coil-change time and setup times between jobs, and we’ve done that.”

Highway Miles

Think about buying or selling a used a car. A big selling point is ‘highway miles.’ Why? A car with more highway than city miles has not been subjected to as many starts and stops, which is consistent with driving in the city. That means less wear and tear on the frame and mechanical components. The same holds true for feed lines.

Continuous-payout feed lines can interface with an analog loop sensor, and, as provided by Colt Automation, for example, control a straightener and/or an uncoiler to run at a constant speed equal to the throughput speed of the feeder, even with a shallow loop.

“Cruising the highway, and using the gas and brake, can cause a lot of problems with your vehicle, and the same is true for your press-line equipment,” Hui offers. “Many lines run that way, with a fast slowdown or startup. But straighteners in continuous-payout feed lines run at constant speeds, matching the feeder throughput speed. You don’t have the pulling and struggling the coil and its inertia. Instead, motion is smooth, which means no downtime to replace the shaft or gears. Feed lines can last much longer due to continuous payout.”

Some feed lines offer simulation functions that can test the line apart from press operation to help ensure smooth material travel.

IoT for Feed Lines

In this day and age, no press-line discussion would be complete without mentioning the Internet of Things, or IoT. Smart technology extends to feed lines.

“Feed-equipment providers such as Colt Automation are incorporating artificial intelligence and IoT into feed lines,” Hui explains. “For example, metalformers with our equipment can use an iPhone or Android smartphone as a jogging pendant. Users can jog an uncoiler, a straightener, a feeder and multiple machines from one device. And, just like smartphones, users can gain machine-control access via facial recognition or fingerprints. In addition, we can even build a customized voice-command library for users who prefer to communicate machines commands in that manner.” MF

 

See also: Colt Automation Ltd.

Related Enterprise Zones: Coil Handling


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