Coil Processing
Tuesday | 01 August, 2006 | 3:36 am

Realizing the future of coil processing

By Lauren Duensing

Back in September 2004, MM covered the installation of a Compu-Cut slitter at an unidentified Midwest service center. That slitter has now been combined with a closed-loop backup control, a CNC leveler and a CNC stacker in an installation at Maryland Metals Processing, Baltimore, Md., to create the ultimate in coil processing technology. In the most basic sense, the line is a multi-blank, cut-to-length line designed to process stainless steel and aluminum.

Jim McKenna, vice president of engineering for Herr-Voss Stamco, describes how all the pieces stack up. "The coil entry equipment includes a four-arm turnstile, a coil car and a payoff reel which feeds the strip through an entry cropping system. The strip is then processed through the Precision Leveler Plus which includes a closed-loop backup control system. The material is then slit by the CNC slitter. The slit mults then exit the CNC slitter into a looping pit. A precision feed roll system then feeds the strip through a high-speed shear where it is cut to length. The slit blanks are then discharged onto a runout inspection conveyor and into a CNC stacking system."

All the pieces come together
What makes this line so special are the capabilities of the CNC leveler, the closed-loop backup control, the CNC slitter and the CNC stacker. All these technologies are state-of-the art. "We built our first CNC slitter about three years ago," says John Gehring, vice president of sales and marketing for Herr-Voss Stamco. "We immediately recognized that we had a hit on our hands."

The first beneficiary of the complete package is Ken McAvoy, president of Maryland Metals Processing. His confidence in the line was so great that he purchased it sight unseen--and he loves it. "I am way ahead of the competition as far as being able to produce a flatter, better product," he notes.

McAvoy points out that the line is especially suited to the surface-critical material his company handles. In fact, according to Herr-Voss Stamco, it can replace your best leveler operator. "The Precision Leveler Plus is the most precise leveler that we've ever designed and built," says McKenna. "The key is the anti-backlash precision ball screw actuators. There is absolutely no lost motion in the machine. Because of that, we're able to use high-performance, variable-speed drives to position the rolls repeatedly and accurately. The machine is so precise that we were able to institute an automatic calibration routine that is all menu driven, completely automatic and done by the operators from the main operator desk. You can calibrate it to the same position, no matter what the roll diameter is after roll regrinds or backup regrinds, and the operators can trust the settings. It also has a punch-and-go auto-set feature. You can call up your different material parameters and set the machine to where it was previously for that material. It gives the operators confidence that the numbers are the numbers," he notes.

The closed-loop backup control also reduces operator error and assures users that the material is flat. "On a leveler you have to adjust your backups to certain positions so you can stretch the material where it is shorter to make it all the same length and take out either your edge wave or center buckle," says McKenna. "Traditionally, the operator has to look at the strip coming out of the leveler and make decisions about what backups to put on or take off. We've developed a laser system that reads the waves coming off the strip, displays on the screen what the different I-units are across the strip and then decides how much the backup should be put on or put off. It prompts the operator to make those moves when it's in manual mode, or you can put it into automatic mode and it will make the moves for you."

This feature allows McAvoy to guarantee his customers that the material is flat. Previously, "I could get a leveling device that was 6 inches or 8 inches long, stick it in from all four corners and tell you that all four corners are within that flatness. But if you said 'is there any residual center buckle in the middle of the sheet,' I would say 'looks flat; sits flat and stable' but I couldn't guarantee it. Now I can guarantee that because of the way the I-units are set across the entire width of the sheet," he says.

Time is money
The machine also saves McAvoy time on each coil he produces. "On my other blanking line, it takes me about 35 minutes from the time I put a coil on the uncoiler to the time I can actually produce a blank. On the [Herr-Voss Stamco] line by the time I've mounted a coil on the uncoiler and broken the band, the entire CNC slitter and the stacker are already set. While the operator is putting it through the leveler to get the flatness, we're putting the disks on the separator to take the strip in and out of the loop, and as soon as it gets to that point, we're ready to go."

That's the beauty of all the technology working together. The design of the line is set up around the main operator station and the main operator desk," says Gehring. "You've got the punch-and-go system on the leveler that is pre-positioned for the material that you want to run. The closed-loop backup control system automatically positions the backup to read the strip exiting the leveler. The CNC slitter is set up from the main desk, and it is completely hands-off. You put your number of mults and widths and other setup data and it prepositions all your slitter knives. At the same time, the CNC stacker's dividers all go to the same position as the knives." So while Maryland Metals Processing is putting a coil on the payoff reel and breaking the band, all the machines are following through with their respective motions, making setup a breeze. "This is a real plus when a customer calls with an emergency," says McAvoy. "If I'm running standard 4-foot-by-10-foot sheets, it is very simple for me to go ahead and run 9.5-inch-by-10-inch blanks. And then I can go right back to doing the 4-foot-by-10-foot sheets."

Return on investment
The ease in setup is only one justification for owning the machine. Gary Hart, president of Herr-Voss Stamco, points out that the company takes a good hard look at justification because "without the customer, there is no Herr-Voss Stamco, and that's been our motto for the 41 years I've been with the company." Each part of the line contributes to the savings.

With the leveler's laser system there is a tremendous savings in scrap loss, Hart notes. McAvoy can then pass that savings on to his customers. "I don't run the cheap stuff; I run stainless and aluminum," he says. Since installing the line, McAvoy has been telling his customers that he levels for free "because the yield that this new line gives us from beginning to end, eliminating the head and tail problems on old pieces of equipment, along with no leveler stops allows them to get more yield and actual weight off a coil."

The CNC slitter also is part of the cost justification because it uses less tooling. For example, "in packed-arbor slitters there are generally two to three heads, but with the tooling and the spacers and the jet nuts, it can cost $50,000 per head for that tooling," Hart says. "We're probably averaging tooling in this machine at about $10,000 to $12,000. Regrind is a third of the price of what the packed-arbors are. The big thing is changing the tooling. We've clocked as much as 16 changes a day with probably about 45 minutes to change out. This machine does it in about 2 minutes." Hart says that the return on investment for the slitter is about 3 years.

For the CNC stacker, the savings comes in manpower. "You no longer have two people setting up the guides in order to receive the blanks coming in. One person sets all that at the operator's desk. We've seen this type of line with up to six people running it. We're down to a person and a half."

"The half of a person is really a material handler," adds Gehring. "Excluding material handling, it's a one-person operation."

With that kind of justification, Herr-Voss Stamco expects the machine to take off. "This is the third CNC system in operation, and Herr-Voss Stamco has additional systems on order for delivery in the fall of 2006, early 2007 and mid-spring 2007," says Gehring. "From our side, it's everything we expected it to be. I think the system that Herr-Voss Stamco has put together with the lasers and the I-units is going to be revolutionary for our industry," McAvoy adds. The machine also provides the efficiency that processors need in order to stay competitive in a changing market. "This line gives me the ability to run more production, better quality--and if I can do anything to save time, time is money--and I can help all my customers to be more competitive worldwide. As a result of installing this line, McAvoy says that he has three or four customers that specify that their material must be done at Maryland Metals Processing, and there isn't a better testament to quality than customer satisfaction. MM

Once a machine is assembled it simply runs. But it takes a lot of engineering on the electrical components to make sure it runs properly. The leveler is now using variable frequency drives on every motor, excluding the lube pump, says Brian Frisk, electrical project engineer. _The encoders provide a million counts per revolution of the motor shaft so that we can position with precision," he notes.

"The slitter has each knife individually driven by a servo motor that has an encoder built right on to the back," Frisk says. "The control loop is closed with a servo drive. Maryland Metal's machine has 15 servomotors on it. They are all working together to put those knives exactly where they need to be. But we don't want to rely on the encoders on the back of those motors because we're talking about splitting thousandths of an inch whenever we're positioning these knives." So, the engineers at Herr-Voss Stamco are making use of a glass scale feedback system. "For every knife we get a position back from a glass scale and we get 10,000 counts per millimeter," Frisk notes--a mind-boggling number even for him.

The stacker is similar to the slitter when it comes to electrics since it uses servomotors to drive each of the separators. "The motors thus far are interchangeable," says Friske. "We're trying to keep a consistent platform."

By Lauren Duensing, from the August 2006 issue of Modern Metals.


















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