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Coil Processing
Wednesday | 04 June, 2014 | 10:38 am

Closing the door on scrap

By Nick Wright

Above: For OEMs, processing coils instead of sheet metal blanks reduces costs, material handling and scrap at the fiber laser cutting process.

With a fast, coil-fed fiber laser, OEM cuts waste and changeover while tripling production time on thin-gauge steel

May 2014 - In his novel “The Lord of the Flies,” William Golding wrote that the greatest ideas are the simplest. When it comes to coil processing lines, whose functionality depends on layers of complex processes working synchronistically, the benefits of removing inefficiencies radiates beyond the coil’s edge. Fiber laser blanking is among coil processing developments that are making manufacturing simple by combining operations and scuttling multiple processes.

The RDI Group, based in Itasca, Illinois, first brought its coil-fed fiber laser blanking system to market in 2011, under the name RDI Laser Blanking Systems and in the last two years the technology has been showing up in more shops. For most RDI customers, the big attraction is improved production time by bundling separate cutting or punching processes into one. That was a key selling point for one of its customers, a manufacturer of hollow metal doors. The company sourced The RDI Group in 2012 after looking for technology that would enhance its coil processing and ultimately give a competitive edge.

Initially, the manufacturer’s team was looking at coil-fed hard tool punching lines because they offered desirable cycle times. After contacting The RDI Group and having the engineers there review the parts, RDI estimated cycle times within the manufacturer’s targets. 

“The major advantage to purchasing a laser as opposed to hard tooling was the flexibility the laser provided,” says the company’s manager of manufacturing technology. “We can change product geometry on the fly without tool changes, and we retain the flexibility to make changes as our product and industry evolves.” By merging coil feeding technology with fiber laser cutting, The RDI Group has dialed in an efficient, continuous parts production feed that boosts productivity, and provides secondary benefits as well.

Welcome savings

At the door manufacturer, its previous coil processing required several steps. First, it would bring in stock slit coils of various widths and run them on a cut-to-length line in large batches to produce steel sheets. Then, the sheets would be transferred to either an NC turret punch press, or a bed-style CO2 laser to cut holes and geometries. The stacks of parts would next be transferred to forming lines for finishing. Many of those steps are now achieved in one fell swoop.

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With the coil-fed fiber laser line, the manufacturer can directly load its slit coils and make parts that are ready for forming in one simple step. This cuts work in process inventory and unites multiple processes into one. The company cuts cold rolled 1008 steel as well as galvanneal in the 14 to 18 gauge (0.048 to 0.075 inch) range. 

The fiber laser provides cost-per-part savings, as well. Cutting speeds for thinner materials are significantly faster when using a fiber laser compared to a conventional CO2. As material gets thicker, the cutting speeds approach those of CO2 lasers. The door manufacturer cuts thin steel, which allows it to take advantage of the difference in cutting speed. 

RDIButton2“With the fiber laser technology, we are cutting at three times the speed we cut with on our late model CO2 lasers,” says the company’s manager of manufacturing technology. “And by taking the material directly from a coil, we are able to really capitalize on that increase in productivity.”

Steve Stultz, sales manager at The RDI Group, explains that the OEM customer makes door frames composed of three pieces—the hinge, latch and header. “What they did before was cut the length of the blanks, so there would be 150 pieces of the hinge side, and then take them to a robotically fed flatbed laser,” he says. Then, robots would take each blank, cut the features, take it out and restack it. Next, the parts would go to a roll forming line or press brake, and lastly operators eventually matched up the three separate parts for welding.

Now, the coil is fed, laser cut and roll formed, rendering finished parts. “We do it as a system,” Stultz explains. “They can cut the hinge side, header and latch, one after another, without restacking it and cutting it again, so we eliminated the working process and gave them sorted parts ready for welding from production.”

In most cases, like cutting stainless and aluminum, nitrogen gas is specified to maximize fiber laser potential, although shop air works for some steel where oxidation isn’t a big concern. The door manufacturer cuts with shop air boosted to an elevated pressure. “We don’t tend to have issues with our finishing processes due to oxide layers,” the customer says.

Servo gains

There is usually some variation among the capabilities of machinery equipped with fiber laser technology as far as cutting speed goes. Even comparing laser OEMs that have the same IPG laser source, which RDI’s blanking laser uses, the speed and rigidity of the cutting head is important to the quality and speed of the cut.

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Coil-fed laser blanking has existed for at least a decade, but The RDI Group is one of the first to appropriate a fiber laser for coil-fed blanking in the U.S., says Stultz. “We completely redesigned how it works in order for it to convey the speed of a fiber laser.”

It’s not only the integration of fiber lasers with coil-fed cutting that separates The RDI Group’s technology from other coil processing advancements, but the controls behind it. Stultz says there are other companies who make versions of coil-fed laser blanking systems, but only this patented process uses a high-speed servo feed in conjunction with the laser. The servo roll feed moves sheet in the X axis, while the laser darts across the Y axis powered by a linear motor. The RDI Group also added an “X prime” axis, which gives the laser an additional 4 inches of travel, “so anything 4 inches and smaller we cut without moving the sheet,” says Stultz. “By coordinating the three axes we can cut faster than if we just used the traditional X and Y axis.”

Combining a quick-reacting servo feed controller with coil feeding reduces scrap, augments material utilization and requires less storage space of material. However, because the blank is a fed coil, it needs to be straightened or flattened, depending on the operation. The door manufacturer in this case uses RDI’s precision straightener to remove moderate coil set, though the width of its coils does not require a leveler. The straightener is a small diameter roll straightener with backup rolls—more than sufficient to flatten the material. 

The alternative is a roll leveler, allowing users to bend rolls left or right to remove defects. The RDI Group’s 1-meter-wide systems come with a precision straightener, while the 1.5- and 2-meter systems come with a leveler. 

Scrap reduction

For any company using a coil-fed laser cutting system, operators are essentially dealing with a 2,000-foot-long nest. Because of the continuous nesting as coil is fed, The RDI Group’s line reduces scrap at the end of the sheet (RDI specifies SigmaNest for its nesting software). Only so many parts can be cut from a sheet, which leaves scrap as an inevitability. With coil, that scrap is mitigated by about 10 percent. The scrap that does get produced drops below through a servo-adjustable chute to a conveyor, leaving operators to attend to other tasks. That fact alone isn’t the only opportunity for savings—it’s also cheaper to buy coil than sheet. Changeover time, as a result, gets whittled down. 

“Even the fastest systems take a good minute or more to change sheet over and cut again,” explains Stultz. “During that time, our machine is still making parts, making it 50 percent faster than a traditional sheet-fed system.” 

The door manufacturer reduced its shifts from three to one and cut its scrap rate. “It’s amazing what it did for them. That’s where you save the money with a coil-fed type laser,” Stultz adds. 

This type of line is best suited for OEM-level manufacturers, with the added benefit of only needing one operator to run the entire system. Smaller job shops and fabricators may still be better off with a sheet cutting system. Nonetheless, when an OEM can merge multiple steps with a newer technology, resulting in reduced scrap, material costs and hours worked, companies of all sizes should take notice. MM

 

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