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Coil Processing
Tuesday | 04 November, 2008 | 7:37 am

More than meets the eye

By Abbe Miller

November 2008 - When ancient explorers looked out toward uncharted territories, the seascape leading up to the horizon looked flat, so radical talk of a spherical world didn’t coincide with what the eye was seeing. As evident when superstitious sailors didn’t fall right off the edge of the earth, their conventional way of thinking was quite wrong.

So can be the case with a sheet of metal. The naked eye can perceive a sheet of steel, for example, as defect-free and perfectly flat. But upon closer metallurgical inspection, perfection isn’t always the case.

What was seemingly flat shows its true qualities the moment a fabricator starts to process it. Internal stresses, referred to as memory, can cause the metal to move, especially if its surface is penetrated. The undetectable imperfections of sheet metal can be problematic when using sophisticated fabricating technologies, like laser cutting, plasma cutting, waterjet cutting, and even stamping and shearing.

"When a laser cuts the surface of a sheet of metal--a penetrating method to cut the stee--it’s like opening a can of soda," says Bob Sipp, director of sales and marketing at Leveltek International LLC, Benwood, W.Va. "You flip the tab up and suddenly there’s this release of energy. The same happens, more or less, with a laser cutting steel that has memory in it. Suddenly, you activate all of that energy."

Meticulous material
Stretch-leveling had been known early on as an effective way to remove visible defects. Since the onset of laser cutting and other state-of-the-art cutting techniques, stretch-leveling technology has steadily increased in popularity as a value-added process for service centers wanting to remove memory from metal sheets and expand a customer base by further meeting their customers’ fabricating needs.

Leveltek International, established in 1997, supplies stretch-leveling systems for retrofit into existing light- to heavy-gauge cut-to-length and coil-to-coil lines or for new, complete lines. The company’s proprietary non-marking gripping systems produce unmarked, zero I-units flat, memory-free material inside and out, both visually and graphically, while enabling unlimited variability in sheet length and part size.

Stretch-leveled material has been proven to perform well with fabricating processes, such as laser cutting, plasma cutting and stamping, for one inherent reason: consistent material. With Leveltek International’s stretch-leveling, the material integrity is maintained, thus, there’s little chance of unexpected warping or buckling.

"All of this metal is connected together--each stretched increment’s buddy is holding on to it, and together they’re holding each other and looking flat," says Nick Yavelak, president of Leveltek International. "Whenever you break those bonds between them, there are unopposed stresses that cause things to pop and move. Let’s think of [a fabricator] who wanted to make a flat metal circle but ended up making a potato chip. The metal was nice and flat, he thought, but as soon he breaks into the stress pattern, the material starts moving all over the place.

"Another aspect [of stretch-leveling] is that in addition to the part not being flat, the laser head is protected from damage," says Yavelak. "The way these new laser machines achieve the highest precision is by positioning the laser head closer to the process metal. The slightest little movement can hit that fragile head and damage it. Laser-head contact with the metal can cause an expensive laser eye replacement, but worse, such an event will shut down the line and stop efficient production."

And increased productivity is another one of the benefits of memory-free steel, no matter the type of equipment involved. Lights-out manufacturing and unattended processing aren’t just buzzwords, they’re requirements in any competitive production setting. If a material’s internal integrity can be trusted, the ability to leave a piece of machinery running on its own is increased.

"Most modern process equipment is PC-based, so programmers and operators want to be able to walk away and program the next machine," says Yavelak. "They want to turn the lights out and let the machines do their work, all the while trusting that the processed material reaches the level of quality required."

Content customers
Del Metals, Brampton, Ontario, a general line service center, is allowing its customers to do just that--trust their material. Last August, it purchased a new stretch-leveling machine from Leveltek International. The machine was retrofitted into its existing cut-to-length line in two weeks.

Leveltek International’s stretch-leveling design provided for an easy retrofit transition into Del Metals’ facility. The Leveltek/Del-specific equipment measures approximately 50 feet in length, so a portion of the cut-to-length line had to be shuffled over. Because Leveltek International’s equipment doesn’t require a hefty concrete foundation, even though it uses millions of pounds of force to stretch the metal, the time involved for installation is minimal.

"If a customer has a piece of processing equipment, he doesn’t want to shut it down for eight to 12 weeks while you’re digging a hole in the ground and filling it full of concrete," says Yavelak. "Any company can continue to exist by stopping their operations for two weeks and call it summer vacation, but they can’t stop their cash flow for eight to 12 weeks and survive." And with the installation complete and the new equipment up and running, Del Metals offers the only non-marking, defect- and memory-free stretch-leveling capabilities in Canada that reach a 72-inch-wide, 1/2-inch-thick capacity, according to Paul LeGendre, vice president of sales and procurement at Del Metals.

"It’s not that our customers weren’t happy with what they were getting," he says. "If anything, 9.5 times out of 10, they were happy with the products that we were shipping. The issue was that there were markets that we couldn’t penetrate because we couldn’t guarantee the flatness of the product coming off of our line. Now, [with the stretch-leveling machine retrofit] we’re actually approved to supply into end uses that were temper-mill only. That’s the competitive edge to stretch-leveling."

Since the equipment was incorporated, Del Metals has run more than 3,500 coils through its line. And the company’s customer base runs the gamut. Garbage bins and tractor trailers are just a drop in the bucket in regard to the end products made from the material Del Metals supplies. Before Del Metals was able to provide memory-free material, the quality requirements from its customers were also varied.

"We don’t know where that pile of steel on the floor is going," says LeGendre. "We don’t know if it’s going to that garbage bin fabricator or to a railcar manufacturer." Del Metals does know, however, that the material it ships is defect-free. Regardless of the level of sophistication, the service center’s customers are discovering the productivity gains that memory-free material can deliver, even if they’re not laser cutting, plasma cutting or stamping.

"Sheets that are flat weld a lot faster than ones that you have to tack weld, pound into place and then re-weld," LeGendre says. "At the end of the day, it has to line up. If it’s wavy, it’s harder [often impossible] to line up and weld than it would be if it’s flat."

With customers seeing the advantages of perfectly flat, memory-free material, LeGendre puts Del Metals’ capital expenditure into perspective. "The fact that we’re staying busy when the market and steel consumption in North America is on the decline--it just goes to show you that if you service your customers and invest in the right technology, good things will happen," he says. MM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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