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How a plate rolling rookie becomes a guru

When a rookie shadows an expert, good communication is key

When shop managers talk about the challenge of finding skilled employees, many outside this business perceive that skill to be rooted in technical knowledge. People on the shop floor do need some technical aptitude, for sure, but don’t spend their days working out complicated trig problems, nor do they study metallurgical chemistries. They make parts. So what do these people need to be successful?

A good place to look for the answer is in the forming arena, an area Ken Pecho knows very well. Pecho is project engineer for Chicago Metal Rolled Products (CMRP), a Chicago contract industrial fabricator that specializes in forming big or complex shapes. Some of the company’s angle rolls dwarf anyone standing near them. The shop has a variety of plate rolls, the largest of which can handle plate up to 2 inches thick and 12 feet wide, depending on the grade and yield strength. This is not an extreme thickness, but certainly thick enough for the vast majority of plate rolling work out there.

The shop’s operators roll sweeping radii for large tank sections and conical workpieces and work with every material type imaginable: carbon steel, all types of aluminum, stainless steel, even duplex steels and armored plate. Recently the company took on a project to roll elliptical, box-welded beam plates—with each section calling for multiple radii—for a casino set to open on the East Coast next year.

In short, these plate rolling operators don’t roll the easy stuff.

People really can’t get this kind of rolling experience in a technical school. So how does a shop like this bring a plate rolling operator up to speed? And in the long term, how does it turn a rookie into a guru? Sure, it involves a rookie shadowing the expert, a practice as old as the industrial age, but what really makes this work?

Pecho said that some people seem to have an innate artistic eye that allows them to pick up the subtleties of plate rolling quickly. But more than that, he pointed to an underlying attribute that really is the bedrock of a successful career in plate rolling: good communication.

In this context, “good communication” doesn’t mean the ability to talk with someone. People can talk all day and not learn a thing. Instead, Pecho described good communication as it applies to three areas critical to plate rolling success, particularly in CMRP’s high-product-mix operation: collaboration, observation, and patience.

About Collaboration

Like at a lot of shops, everyone at CMRP is cross-trained on different processes. An operator may run an angle roll in the morning, perform some prebending on a press brake, and help with the plate roll in the afternoon. As Pecho explained, knowing other processes helps build a foundation for sheet metal and plate forming in general.

But also like a lot of shops, CMRP has its specialists, people who can operate multiple machines but spend most of their day on one. Managers have identified plate rolling teams, each consisting of one experienced and one less experienced person who work together well. This doesn’t necessarily mean a plate rolling veteran needs to be verbose or a master explainer, the traditional attributes of how we define a “good teacher.”

Managers instead look for a good connection. It really boils down to personality types. A veteran may have a gruff or curt style and a less experienced person may be easygoing, but the opposite styles sometimes gel—and when that happens, managers make sure the two work together as often as possible.

Project Engineer Ken Pecho (on left) works with a plate rolling team to check the radius of a rolled workpiece.

“When you see there’s a connection, it’s almost as if these guys are reading each other’s minds,” Pecho said. “When one guy is coming to a complete close [of a cylinder], the other guy is setting up the plasma cutter to trim the ends [to eliminate the flat section near the seam of the rolled workpiece].”

For most new jobs, Pecho and other project engineers walk to the floor and talk with operators about how a certain job is to be rolled. And at CMRP, operators aren’t just rolling A36 steel to a single radius. They’re working with duplex steel, various grades of aluminum and stainless, and often they’re not rolling straightforward cylinders. They’re rolling cones. They’re rolling elliptical shapes with multiple radii.

When working with elliptical and other complex shapes with multiple radii, engineers and operators talk through the CAD drawing, segmenting the infinitely variable radius in the original file into defined radius segments, each tangent with the next, ensuring that the final product looks entirely smooth with no bend lines. The veteran operator then makes the proper radius adjustments at just the right places, and the rookie watches and learns.

“No bend lines and no flats” in a rolled workpiece is CMRP’s modus operandi. Most jobs, even those with multiple radii, emerge from the plate roll with no noticeable bend lines between different radius segments. Some amount of flat is unavoidable—the plate roll needs something to grab on to—but in most cases CMRP tries to eliminate or minimize it.

The flat section at the seam becomes more noticeable the tighter you roll. Operators may roll a plate that’s a little longer than needed so that they can trim the ends with a plasma cutter. Or, if the customer doesn’t want to pay for a little extra material (understandable with duplex steel and other pricey plates), operators may prebend the plate in a press brake to minimize the flat section to where it’s barely if at all noticeable.

About Observation

At CMRP, a rookie becomes a guru by taking note of all these idiosyncrasies. Good observations lead to good questions and, ultimately, good information, which goes into a rookie’s notebook.

The rookie may listen to a veteran talk with engineers, who discuss the fact that the plate needs to be taken over to the press brake for prebending. This time the operators have excess material to work with, so they could trim the ends. Why move it to the brake for the initial bends?

The rookie ultimately finds out that the material, well over an inch thick, exceeds the plate roll’s tonnage limits for prebending. He learns that it takes far more tonnage to prebend than to roll this particular material at this radius, and he makes a note of it in his notebook.

Working with the veteran, he stretches a string across the plate edge coming out of the plate roll. If any light shows from underneath the string, he knows that there is (most likely) some crowning issue that needs to be addressed.

The company usually can process a plate with a properly crowned top roll, with the right-sized bulge in the center, farthest from the machine side frames. But because CMRP processes an extremely wide range of materials, adjustments for crowning are sometimes unavoidable, and quite often this involves using shims, anything from thin sheet metal to pieces of cardboard.

Crowning problems usually make themselves apparent in the prebend. A downward bow in the center, called barreling, points to insufficient crowning, with the radius tighter on the sides than in the center. If the operator can’t adjust the rolling pressure, he needs to resort to shims, placing them toward the center.

A prebent plate edge bowing upward in the center is a sign of excessive crowning, with the radius in the center tighter than on the edges, producing an hourglass shape. So shims may need to be used again, this time near the edges of the workpiece, toward the machine frame.

Operators continue to measure the initial radius with radius gauges, taking into account any holes or other windows cut into the material. As Pecho explained, cutting those windows with a plasma or oxyfuel torch may or may not have a significant effect on the final radius. It depends on the material, radius, and location and orientation of the window.

“If [the window is] perpendicular to the roll direction, it’s usually not that bad,” he said. “But when it’s parallel to the roll direction, the piece may not take the radius, and you may get a kink in your material.”

Operators observe the effects of gravity on the workpiece and know the importance of using side and overhead supports. Without support, the material kinks and stretches. This applies not just for cylinders, but for other rolled shapes as well.

For instance, CMRP rolls a fair amount of large tank sections that are field-erected. These aren’t cylinders but instead are gradual, sweeping radii that can extend 20 or 30 ft. outside the machine. “These may be 0.25 in. thick and 120 in. wide,” Pecho said, “but they’re often more than 30 ft. long.”

In these cases, rookies fetch some of the company’s cranes with under-the-hook lifting devices designed to handle these extremely large workpieces emerging from the plate roll. This ensures that these massive curved sections maintain their shape throughout the rolling cycle without stretching or kinking the material.

“You never want to stretch the material,” Pecho said, “or it’s over. You’re not going to get that kink out of the material, and no matter what you do, you will not get that perfect, smooth radius throughout the piece.”

High-yield material can exhibit high amounts of springback. A radius may look ridiculously tight coming out of the plate roll; but as the radius is formed, it springs back significantly.

Pecho added that getting springback right relates to good communication between engineers and the plate roll operators. The company uses software to predict springback, relating the material thickness and grade with the forming radius at hand.

“We roll plenty of A36 carbon steel, but we also work with grades like A514 and AR400, even duplex material,” Pecho said. “AR400 really looks crazy when it comes out of the machine. If you didn’t understand material behavior, you would see it and think that it was way off, that there was no way it was going to roll to the desired radius. But it really does spring back a tremendous amount. Operators really need to have an understanding of what the yields are and how they affect rolling characteristics.

“We really need to aim for this initial radius for the material to spring back open to the desired radius,” Pecho continued. “Having an operator who understands material and understands how the material is going to react as it comes out of the machine—that’s all critical.”

About Patience

Over weeks and months of observation and collaboration, the rookie learns about different materials, from the extraordinary springback of AR400 and the significant springback of 6061 aluminum, to the “pancaking effects” excessive rolling pressure can have on softer aluminums.

Pecho added that rolling aluminum brings another critical aspect of the plate rolling operation to the fore: patience. A new operator may be tempted to underbend and then reroll the piece to the right radius. Of course, this not only takes more time, but it also work-hardens the workpiece—and aluminum exhibits work hardening like no other material.

At CMRP, it’s extremely important to get the initial radius as close as possible to perfect, Pecho said. This not only minimizes work hardening (not just on aluminum but all material), but it also makes the entire operation more efficient. They reroll only if it’s a customer requirement or when there is no practical alternative.

Knowing this, CMRP doesn’t assign rookie operators to operate the machine for challenging materials or part geometries. Instead, most rookies make the shift—from helper and observer to the person actually operating the machine—on simpler jobs.

For these, the rookie may require a little hand-holding. But as Pecho explained, if that person has observed, taken notes, and learned the basics of the craft, the transition usually isn’t that difficult.

Still, for the transition to be successful, the operator needs to be patient. If he dives in and attempts to roll a plate as quickly as his veteran counterpart, problems arise. The operator watches the initial radius forming. The operator watches the initial radius forming and reaches for his radius gauge to ensure the material is forming and springing back to the proper radius.

Rolling is an art that requires patience, and passing on the torch to the next generation is also a patient affair. In a world of automation and computer control, so much of plate rolling remains a craft. It’s a matter of taking notes, asking questions, and learning the craft so that one day the rookie becomes the guru, ready to pass on the torch to the next generation.

Photos courtesy of Chicago Metal Rolled Products, 3715 S. Rockwell St., Chicago, IL 60632, 773-523-5757, www.cmrp.com.

About the Author
The Fabricator

Tim Heston

Senior Editor

2135 Point Blvd

Elgin, IL 60123

815-381-1314

Tim Heston, The Fabricator's senior editor, has covered the metal fabrication industry since 1998, starting his career at the American Welding Society's Welding Journal. Since then he has covered the full range of metal fabrication processes, from stamping, bending, and cutting to grinding and polishing. He joined The Fabricator's staff in October 2007.