Technology Spotlight: A recipe for scaling up laser cutting power

Marcin Ejma remembers the first time he saw a fiber laser. It was near the end of a long European tradeshow in the mid-2000s, when he and his business associates sat down on a bench and looked across the aisle at the IPG Photonics booth.

“I saw the words in front of me, ‘fiber laser,’ which meant nothing to me. But then I talked with them, and after 10 minutes I understood that this was the future,” Ejma recalled. “I knew that if the fiber laser could cut, it would solve 70 percent of the maintenance problems we were having with CO2 laser systems.”

During the years before that fateful tradeshow, Ejma had run a company dealing and servicing second-hand laser cutting machines. But after seeing the fiber laser, he changed course entirely and in 2008 opened Eagle, a designer and manufacturer of fiber laser cutting machines based in Poland.

What makes fiber laser cutting so intriguing is the productivity potential associated with greater and greater power levels. After all, other industrial applications such as welding have put 100-kW fiber lasers to use. Surely, one extremely powerful fiber cutting laser could replace multiple CO2 lasers, right? One could imagine a fabricator with just a few high-powered fiber lasers with material handling automation. A quick shuttle table loads and unloads parts, while cut sheets are transported to an area that feeds vast quantities of press brakes and other downstream operations.

This sounds great in theory, but the idea has two challenges. The first involves designing material handling automation to ensure sheets are loaded and unloaded quickly. After all, what good is a fast laser machine if the system sits idle waiting for material? The second involves the laser machine itself, including the construction, the drive technology, and, not least, the cutting head optics.

Put another way, a fiber laser can provide the power, but the machine needs to be designed to keep up with that power. That, Ejma said, was the idea behind Eagle’s iNspire laser cutting machine, introduced last year at EuroBLECH in Hanover, Germany. It’s available in laser powers up to 15 kW.

The company’s booth showed a cut sample of 60-mm-thick stainless steel—or more than 2 inches. But as Ejma explained, the larger market for the machine will be for efficient cutting of midrange material, such as 0.25 and 0.5 in. thick. And of course the laser can move very quickly through gauge material.

Still, according to Eagle, to make a real difference in a laser cutting operation, the system design has a few requirements. The machine can be connected to material handling towers, of course. But outside the machine itself, the system also needs pallet changers fast enough to keep up with the laser. According to Eagle, its servomotor-driven, chain-linked pallet changer can swap out in 9 seconds.

Inside the cutting space, the system needs drive motors to accelerate the head; the Eagle system has direct-drive linear motors in X, Y, and Z and offers 6 Gs of acceleration.

“Every time you double the Gs, the time and distance it takes to get up to speed goes down by half,” said Chip Burnham, co-founder of Maple Valley, Wash.-based Fairmont Machinery, which began representing Eagle in North America last year.

Of course, all that acceleration can create a lot of vibration. To mitigate this, Burnham said that the machine is built with vibration-dampening characteristics. The machine base is made of polymer concrete. “It’s the same material used in coordinate measuring machines.”

All those Gs are driving a traverse bridge made of carbon fiber material. On that bridge is the cutting head that, according to Eagle, has been designed to handle 15 kW of power. This applies to the head’s light weight (it wouldn’t make sense to design a lightweight bridge if the cutting head weren’t light too), as well as the head’s structure and optical characteristics.

Fiber laser cutting head optics are extraordinarily sensitive, especially in the higher power ranges. One ever-so-tiny spec of contamination on the cutting head optics can cause serious problems when connected to an ultrahigh-power laser.

To prevent contamination within the head, Ejma explained, the company designed a cutting head with no moving parts on the inside. “At the same time, we can change the focus diameter and focus condition in the head without those moving parts.”

Ejma said he couldn’t reveal the specifics behind the technology for competitive reasons (the head design is patented). Still, anyone who uses the laser will notice something different when they change out the head’s protective window: it sits more than 14 in. above the nozzle. That increased distance is designed to protect the window from contamination that can come from the piercing and cutting process—the result being that the operator shouldn’t have to replace the window as often.

In fact, replacing that protective window (or cover glass) frequently creates further complications. As Ejma explained, “From our analysis, we see a lot of cutting head failures happen because of incorrect operation. The operator may not be trained, or maybe he’s having a bad day, or perhaps he just can’t see that he’s putting contamination on the inside of the cover glass. And what happens? It doesn’t stay on the cover slide, but instead gets sucked up and sticks to the optical elements.

“Because this cutting head design has no moving parts, there’s much less risk of this happening. If the operator makes a mistake and leaves contamination on the [inside of] the cover slide, the contamination stays on the cover slide.”

No moving parts” seems to be a common motif in the fiber laser world. The fiber laser power source has no moving parts, and now the cutting heads themselves don’t need to have moving parts either. Such a motif may be key for fiber laser cutting power to scale up into the stratosphere.

Fairmont Machinery, www.fairmontmachinery.com

Eagle, www.eagle-group.eu