June 17, 2008
How can laser technology make metal fabrication more efficient? The efficiency comes not only from advances within the laser itself, but also in new ways to integrate those lasers for optimal part flow on the shop floor. Several presenters at ALAW 2008 hammered this point home.
Among all metal fabrication technologies, lasers stand apart. Within just a few decades, they've moved from an obscure curiosity to a driving force in manufacturing. For job shops, just having a 2-D laser cutting system used to be a competitive advantage; today laser cutting pervades industry. For welding, hybrid technologies—a laser combined with another joining method, such as wire or plasma arc—have helped alleviate concern about gap tolerances and the need for precision fit-ups. Remote laser welding, in which standoff distances can be measured in meters, is delivering previously unheard-of throughput. Laser brazing has emerged at automotive OEMs and elsewhere. And fiber technologies, which could make manufacturing with lasers even more flexible, are now moving full-force into the marketplace.
Although industrial lasers have changed at breakneck speed, one question manufacturers ask hasn't: How can laser technology make metal fabrication more efficient? The efficiency comes not only from advances within the laser itself, but also in new ways to integrate those lasers for optimal part flow on the shop floor.
Several presenters at ALAW 2008 hammered this point home.
More than 200 engineers and metal fabricators gathered May 13-15 in Plymouth, Mich., for this year's laser conference. Launched in the early '90s as the Automotive Laser Applications Workshop, the event has since broadened its scope to include laser applications in contract manufacturing and other OEM sectors like aerospace and off-road equipment. Organized by the Laser Institute of America and the Fabricators & Manufacturers Association, the conference consisted of two concurrent programs, an automotive track and a fabricators track.
Within the fabricators track, presenters focused not only on new technologies, but, perhaps even more important, on effective ways to implement those technologies on the shop floor.
For instance, conference speaker Jeff Adams spoke of an ambitious goal he had back in 2003. The president of Laser Precision LLC, Libertyville, Ill., wanted to compete globally, and the way to do that was to take labor out of the equation."We wanted to put ourselves on a fair economic playing field with some of the low-labor-cost countries," he said.
Until 2003 the company used laser cutting systems that required manual intervention. Spark-on time was 85 percent; today, after integration of four automated, 4-kW laser cells with automatic material handling, it's 97 percent. Those machines run 24/7 and are manned only one shift a day by one operator; everything else is unattended.
Adams added that the shop didn't necessarily look for the highest power or the fastest machine. Machines with thermal stability, running at less than maximum power, usually win out for unattended production, he said, for the same reason the tortoise beat out the hare. Consistent, albeit slower, cutting overnight gives greater throughput than a blazingly fast laser cutting system producing bad parts all weekend.
"My greatest fear is to come in on Monday and see a bunch of scrapped parts," Adams said.
Adams tallied some basic considerations for selecting a laser system for unattended work: beam stability; network connectivity; height sensor on the laser head; minimum overall maintenance requirements; purge mechanisms that keep contaminants out of the beam area; as well as automatic reordering of assist gas, whereby suppliers monitor and replenish the gas as soon as it reaches a certain level."The last thing you want to do is run out of assist gas over the weekend," Adams explained.
He added that parts pushing the machine's envelope should be run during the manned shift."If your machine can process up to ¾-inch material," he said,"you don't want to process ¾-inch material unattended."
Parts with complex geometries requiring excessive piercing can present problems, as well as parts that can't be easily tabbed."Identifying parts can be very confusing," he explained."We run about 4,200 different part numbers, and many of those parts have similar configurations." To avoid confusion, nest identifications are laser-etched on the sheet, so when operators remove tabbed parts, they can compare them to the original nest program.
Adams also recommended that fabricators pay attention to the small things, too, elements that become not quite so small if they cause a machine to crash overnight. For instance, he recommended pointed-slat tables to handle any slug welding that may occur. A laser-cut slug may attach to the slats on the table, creating an apex that will cause the next part to tip.
At Laser Precision, shop managers went a step further."We incorporated nonferrous slats," Adams explained."Because of the slug-weld issue, we used copper slats, because the mild steel does not effectively weld to copper."
Integrating efficient, lean laser operations does require attention to detail— like those pointed, nonferrous slats— but according to conference speaker Eric Borman, president of Progressive Metal Manufacturing Co., Ferndale, Mich., equipment detail represents only part of the equation in implementing a lean operation."The equipment portion is about 10 percent of getting there," he explained."Getting people onboard … is the big majority of it."
Put another way, automated laser systems mean little without the right people getting the most out of them.
Progressive Metal, which started as a small job shop in 1962, invested in its first laser in 1998. In 2002 the company held its first lean kaizen event."Frankly," Borman said,"we fell on our face. Nothing substantial happened with lean until 2007."
It was then that the company performed a thorough cost and plant layout analysis. Instead of positioning the laser in the middle of the floor, away from downstream bending and welding operations, the company moved those secondary processes next to the laser, promoting efficient part flow.
Near the end of his presentation, Borman showed a series of three photos, one from 1972, one from 2002, and one from this year. The 1973 and 2002 images were virtually identical, with racks of work-in-progress (WIP) and raw stock everywhere. In the recent photo, those racks aren't there.
"We were a $4 million shop in 1998," he said."In 2007 we had $28 million in sales, and that includes us working with the likes of Ford and GM. We endured the price-downs, and in the exact same square footage we have three times the amount of work."
Modern equipment is part of it, Borman explained, but the worst thing a shop can do is buy an automated laser cell only to create a bottleneck of WIP downstream.
"We're a job shop, and in a job shop there are certain types of lean that work. We are a flow-based manufacturer. We're concerned most how parts flow through the floor. Our objective: We want to get to the point where we can make a part and ship it in seven days— no matter what."
Randolph Paura, Canadian regional manager and processing consultant for Oxford, Mass.-based IPG Photonics, reported that a company in Europe has successfully implemented mobile orbital pipe welding using a 20-kW fiber laser. The technology reduced personnel needs by 90 percent.
Gregg Simpson, president of Ohio Laser LLC, Plain City, Ohio, offered practical tips to expand a shop's capability using a 3-D laser. For instance, consider an operation requiring two 90-degree bends and several holes. Instead of cutting holes and then bending flat sheet in a press brake, a fabricator can create the part using a box tube, if the correct size is available. The laser can cut the holes and cut off the top portion—all in one setup.
Rich Martukanitz, Ph.D., of the Penn State University Laser Processing Consortium, State College, Pa., reported work on technologies that, among other things, relieve the gap-tolerance challenges of pure laser beam welding. Among them is laser stir welding, in which the laser beam oscillates at a rapid frequency.
Michael Poss, senior manufacturing project engineer for General Motors, reported on a recent study the auto giant performed on laser brazing, using a laser to melt a bronze filler wire, for exterior roof-rail joints of certain high-end vehicles. The traditional method involves a resistance spot weld hidden by a molding. The laser braze produces a cosmetically smooth joint, so smooth that it eliminates the need for moldings and the adhesives they require.
For those serving the automotive business, Jon Jennings, business development manager for EWI, Columbus, Ohio, had this to say: "Get used to it. You're going to be working with materials you haven't heard of before … and we're going to have to weld dissimilar materials. You can't bolt it all together." Jennings' talk focused on an EWI study about future trends in automotive structures. He said that demand will rise for alternative materials—like advanced high-strength steels, aluminum, and magnesium—as well as alternative joining methods, such as adhesive and weld bonding.
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