A Case Study in Slitting Thin-Gauge Specialty Metals
By the Staff of Metal Center News
Not all slitting lines are the same. Those designed to slit very thin-gauge metals require special features to deliver four-decimal precision, like the new line at ATI's Flat Rolled Products facility near Chicago.
Allegheny Technologies Inc., a global producer of specialty metals, recently consolidated its Chicago-based flat-roll processing operations into the new ATI Chicago facility in Bridgeview, Ill.
ATI is commissioning a new Hot Rolling and Processing Facility in Brackenridge, Pa., that will be able to produce wider, heavier and thinner coils. As part of the company’s overall strategy, the ATI Chicago operation needed to upgrade its equipment to take advantage of these new capabilities. Today, the Bridgeview facility houses four slitting lines, including a new workhorse from Burghardt + Schmidt.
Machine maker Burghardt + Schmidt, based in Remchingen, Germany, has been in business since 1947. But all of its U.S. installations to date had been with German transplant companies until this new line at ATI. Burghardt + Schmidt now has a U.S. sales director in Peter Swenson, whose office is in Chesterton, Ind. "Unless you have a U.S. face, companies are reluctant to deal with you," he notes.
The ATI Chicago facility processes mostly stainless steel and nickel alloy flat-roll, all sourced from the company's Flat Rolled Products Group mills in the Northeast. The new facility offers several safety, cost-saving and logistical advantages to its previous location and provides customers with more consistent material, explains Cory Hextall, manager of operations. It has five bays including two drive-through bays that allow trucks to bring material directly into the building. "It allows us to drive trucks in and pick coils right off the trailers. It’s just a lot more efficient and safe," he says.
The new Burghardt + Schmidt line can handle coils up to 62 inches wide and 66,000 pounds with gauges from 0.004 to 0.060 inch. It features entry and exit crop shears; a mobile strip braking unit that maintains the proper tension; an entry dancer roll unit that provides precise micro tension to the strip prior to the slitter head, enabling complete strip guiding control; a large-diameter slitter arbor with CNC controls designed to counter deflection and provide accurate and consistent knife penetration; a four-arm rotating capstan for rapid tooling changeover; and a dual mandrel turret-style recoiler for quick turnaround.
The line's 1,500 horsepower--split between the uncoiler, slitter head and recoiler--provides for smooth, quiet acceleration and deceleration at very high speeds. Use of AC gear motors rather than hydraulic motors to power most machine motion provides better control and more accurate repeatability, claims the line's manufacturer.
Burghardt + Schmidt designs its slitting lines to meet especially tight thin-gauge tolerances, which helps keep burr and other parameters to a minimum, Hextall says. “That is one of the main reasons we went with B+S, because they specialize in processing really light-gauge metals.”
The precise tolerances achievable with the new slitting line will help ATI better meet the needs of demanding customers by keeping edge burr consistent along the same edge and from edge to edge. These tight tolerances also help deliver product with burr well below the industry standard of 10 percent.
For greater efficiency, the new slitting line has an offline setup turret with four arbors that allows operators to set up three other jobs while one is running. When one job is complete, the turret rotates the new tooling into position for the next run. "It can take significant time to load the knives and spacers on each arbor when setting up for a large number of mults. So performing that task offline while the slitter keeps running is a major time-saver," Hextall says.
The line is designed for similar savings on the exit end, which is equipped with a dual mandrel turret-style recoiler. "With the dual recoiler, we can rotate the turret as soon as the strips are cut by the exit shear. This allows operators to apply identification labels to the mults and tape down the ends while the slitter is processing the next job. This is especially important since the line can slit up to 50 mults," Hextall says.
Hextall and Swenson point with some pride to the safety features of the new line. It has full perimeter guarding with solenoid interlocked access points that prevent operators from opening gates while the machine is running. "Very few slitting lines in the industry have full perimeter guarding blocking access to the strip the entire length of the slitting line during coil processing. That was a point of emphasis for us during the selection phase of the project," Hextall says.
To prevent hand injuries, a strip clamp on the exit side of the slitter head grabs the slit mults at the looping pit and delivers them to the recoiler mandrel. "This helps the operator by clamping and moving the slit strands from the slitter head all the way back to the recoiler so the operators have minimal contact with the strip," Hextall says. "Most injuries happen to workers' hands when they reach into a machine. We always try to use no-touch tools. With this clamp device, there is almost no need for anyone to touch the strip during the threading process."
The installation process for the slitter was also innovative. Once Burghardt + Schmidt completed the components of the line, it assembled the main pieces at its plant in Germany, then invited ATI to visit. "We had a factory acceptance test in Germany. We visited B&S for initial testing and most of the machine run from uncoiler to recoiler. It is one thing to look at it on paper, but a whole other thing to actually see it in operation," says Hextall. Then the line was disassembled and shipped to the U.S., where ATI's contractors reassembled it. All its electronics were pre-installed in a shipping container, which greatly simplified the process of wiring and powering up the line. The climate-controlled container now serves as the line's control room.
Installation began in mid-December 2012 and was largely completed just six weeks later. ATI declined to comment on how much it spent on the new slitting line but did mention that it was cost competitive. "It was all hands on deck. We had guys working through the holidays. This was probably one of the fastest installations I have ever been around," Swenson says.
|ATI Chicago Slitter
Manufacturer: Burghardt & Schmidt: 0.004 to 0.060 inch
Material thickness: 0.004 to 0.060 inch
Material: Stainless steel and high nickel alloy
Line speed: Up to 1,500 feet per minute
Coil weight, uncoiler and recoiler: Up to 66,000 pounds
Coil ID range: 16 to 24 inches
Line width (nominal): 60 inches
Line mode: Power payoff with double loop, via dancer arm control
Pit depth: 50 feet
Slitting capacity: Approx. 50 strands of 0.008 inch, 30 strands of 0.030-inch stainless steel