The rise and rise of the fiber laser

The fiber laser has many advantages over the carbon dioxide laser.

FIGURE 1. CO2 laser light creates a smooth cutting front, which automatically produces a high-quality cut edge [1].
FIGURE 1. CO2 laser light creates a smooth cutting front, which automatically produces a high-quality cut edge [1].

JOHN POWELL

Way back in the mists of time, the laser cutting market was completely dominated by the carbon dioxide (CO2) laser. These had progressed from laboratory toys to industrial machines in the 1970s and 1980s, and by the 1990s, they were multikilowatt plug-and-play devices with a high level of reliability. By the turn of the millennium, the laser cutting industry was generally considered to be mature and growing steadily. No one was expecting any major steps forward in the technology by that point.

So, around 2006, I was not alone in being highly skeptical of the claims salesmen were starting to make about a revolutionary new laser cutting technologythe fiber laser.

Early results from these new lasers were interesting, but patchythey were probably going to overtake CO2 lasers for cutting thin-section (3 mm and below) steel because they cut faster, but in thicknesses above ~5 mm, the surface quality was well below what we’d come to expect from the CO2 machines.

Experts like Dirk Petring1 got to work on why the cut quality on thicker sections was inferior and soon found the answer. In the case of CO2 lasers, the cut front was smooth and so the liquid metal flowed downwards in a very orderly way (FIGURE 1), leaving only minor ripple patterns on the cut edge.FIGURE 2. The 1 µm wavelength light from a fiber (or disk) laser bounces around inside the cut zone, creating hot spots and bumps on the cutting front [1].FIGURE 2. The 1 µm wavelength light from a fiber (or disk) laser bounces around inside the cut zone, creating hot spots and bumps on the cutting front [1].

In the case of fiber lasers, the different wavelength of the light meant that the laser beam bounced around a lot more inside the cutting zone (FIGURE 2), creating hot spots and little bumps on the surface of the melt as it flowed down the cut front. These hot spots and bumps resulted in a much more turbulent, fluctuating melt flow, leaving behind a rougher cut edge (FIGURE 3) that got progressively rougher at thicker sections.FIGURE 3. The hot spots and bumps on the fiber laser cutting front produced a rougher cut edge until R&D teams at a number of firms and institutions developed techniques to tackle the problem [1].FIGURE 3. The hot spots and bumps on the fiber laser cutting front produced a rougher cut edge until R&D teams at a number of firms and institutions developed techniques to tackle the problem [1].

Once the problem had been identified, the applications team at IPG Photonics (who developed the fiber laser) got to work to come up with answers. They and similar teams at firms such as Bystronic, Salvagnini, Mazak, Mitsubishi, Kimla, and Cincinnati, who use IPG Photonics lasers in their cutting machines, and Trumpf (who had developed the disk laser which, from the point of view of cutting, is very similar to the fiber laser) created technological answers that resulted in cutting qualities comparable to (or even better than) CO2-quality cuts (FIGURE 4).FIGURE 4. High-quality cut edges are now possible in thicker-section metals.FIGURE 4. High-quality cut edges are now possible in thicker-section metals.(Photo courtesy of IPG Photonics)

With cutting quality under control, fiber lasers were now on a roll. This is demonstrated by comments made by Dave Larcombe (the then-managing director of Bystronic UK) in the April 2017 edition of Machinery World. In this article, Dave stated that for the last year and a half, Bystronic had not sold any CO2 lasers, but sales of fiber lasers were doing very well. My own experience confirms this, as the last two lasers my company bought were fiberand the next one will probably be another fiber. The trend towards fiber lasers is also clear from the literature on the subject. In 2008,  I wrote the LIA Guide to Laser Cutting,2 which included only a tiny section on fiber lasers. The most recent version of this book, The LIA Guide to High Power Laser Cutting,3 written in 2017 in collaboration with Dirk Petring, Jetro Pocorni, and Alexander Kaplan, devotes about half of the book to fiber lasers. The following TABLE, taken from the guide, shows the increased speeds at thin section, which a fiber laser can achieve when cutting stainless steel (these results are not for a particular model of laserjust generic 5 kW machines).2009 Ils Pow T

As most laser-cut stainless steel is below 6 mm thick, it is easy to see that the speed advantages of the fiber laser are commercially important. Similar (or better) improvements in productivity are also possible with non-ferrous metals and carbon steels. The only place where the fiber laser falls down is in the cutting or engraving of plastics and wood-based materials because 1 µm wavelength light passes straight through these materials.

In addition to increases in productivity, the fiber laser has other advantages over CO2 laser technology, including:

  • Reduced energy consumption, as fiber lasers are more electrically efficient than CO2 machines.
  • Reduced start-up time.
  • Reduced physical footprint because the lasers are smaller (although the cutting tables will, of course, be the same size).
  • Reduced maintenance downtime, largely because fiber lasers don’t have moving parts such as vacuum pumps and blowers, which are incorporated into CO2 machines.

In the early days, there were problems with the cost of parts that broke down on fiber lasers, including the fiber connectors and the modules of diodes that power the machines, but these have largely been dealt with as a result of improved reliability and increases in warranty periods.

Given all these advantages, it’s not surprising that fiber lasers are ruling the roost. It seems that, in the UK at least, the future of the CO2 laser will be confined to the niche market of cutting or engraving plastics and wood-based products.

REFERENCES

1. D. Petring, T. Molitor, F. Schneider, and N. Wolf, Phys. Procedia, 39, 186–196 (2012).

2. J. Powell, LIA Guide to Laser Cutting, 2nd Edition, ISBN 9780912035161 (2008).

3. J. Powell, D. Petring, J. Pocorni, and A. Kaplan, LIA Guide to High Power Laser Cutting, ISBN 9781840168111 (2017).

Dr. JOHN POWELL (john.powell@laserexp.co.uk) is technical director of Laser Expertise Ltd (Nottingham, England), which he co-founded in 1984. He is the author or co-author of three books on laser cutting, the latest of which is the LIA Guide to High Power Laser Cutting.2

EDITOR’S NOTE: This article was reprinted from The Laser User, Issue 93 (Summer 2019), with permission from the author and The Association of Laser Users (AILU); ailu.org.uk.

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