DIODE LASERS Te company is currently shipping 6kW diode


systems; it introduced an 8kW laser at Euroblech that will begin shipping next year, and Pandey said the technology can power scale, and will reach 10kW in the near future.


Competing with fibre Mazak adopting Teradiode’s systems is testament to direct diode lasers’ ability to cut sheet metal, but it’s still an incredibly young technology. ‘Right now, in my eyes, it’s still a little too early for high brightness direct diode technology for cutting,’ commented Biesenbach. Coherent’s product line manager, Klaus Kleine, added: ‘Diode laser systems made for very high brightness applications less than 20mm-mrad look very complex to me.’ Kleine continued: ‘I believe that the best


brightness converter is still the fibre laser. Te fibre laser seems to be the more elegant solution for now. I expect that to change, but it will take time.’ ‘Fibre lasers have a hold on the 2D cutting


market,’ said Pandey. ‘What we learned from our customers – machine builders – is that moving to a different technology, and even to a different power level, requires a lot of effort from their side – all the different cut parameters and recipes that they have to test. It’s a fairly big investment for machine builders and they have to do a lot of qualification work, building machines in the lab and testing prototypes. It’s probably a six-month- to-a-year runway to adopt this technology. ‘If you look at the installed bases using direct


diode lasers, it’s very small,’ he continued. ‘Diode reliability is at the heart of our whole system. We think reliability is good enough to be made at an


industrial scale. Aſter that it’s the type of application that really matters, as to where the technology fits in.’


Hardening, cladding and brazing At the moment, the dominant applications for industrial direct diode laser systems are areas like hardening, cladding and brazing. Tese fields need very high power, up to 10kW, and use low beam quality in the range of 100mm-mrad. ‘Laser cladding and hardening, a big market in


Asia, is also growing in Europe,’ Biesenbach said. Hardening and cladding need specific homogenised beam shaping. In addition, the wire or powder supply has to be integrated with the laser beam in cladding applications. By contrast, brazing has a similar beam parameter product as cladding, but the systems contain more instrumentation; they need a scanner and more process experience to operate. Tese are the classic fields for diode lasers, for which Dilas has been supplying lasers since the year 2000. Coherent-Dilas offers 3-10kW direct beams for


cost efficient tooling for the big cladding markets. Higher quality diode laser systems are fibre delivered – Coherent-Dilas offers 6kW and 8kW fibre-delivered units. In China, for example, certain galvanic plating technologies are being substituted with laser cladding in the mining industry, which is a big market. Coherent-Dilas uses standard 10mm high-


power diode bars in its highest power diode systems. ‘Tis is the cheapest way to generate


photons in the laser business,’ commented Biesenbach. For higher brightness between 10-30mm-mrad, the company uses a different laser diode chip, called a Tailored-Bar or T-Bar. ‘Te T-Bar sits between an economical,


best brightness converter is still the fibre laser


I believe that the


powerful but low brightness bar, and the high brightness single emitters,’ explained Biesenbach. It is a combination of several emitters on one monolithic chip – Coherent-Dilas puts five emitters on one chip. Tis means all the processes involved in producing T-Bars, such as incorporating optics, is a factor of five more cost-efficient compared to a single emitter. A diode laser system made of T-Bars can give 1kW single-wavelength laser power at 20mm-mrad beam quality, which is a good tool for sheet metal welding, according to Biesenbach. ‘Te charm of welding with a diode laser is that the seam is


cosmetically almost perfect,’ Biesenbach said. Welding with a diode laser is very forgiving in terms of tolerances. Kleine added that Coherent’s 4kW diode laser using a 600µm fibre at 0.1 NA will ‘perfectly replace lamp-pumped lasers for many welding applications, even keyhole welding.’ Te laser typically has a working distance of around 200mm with a spot size of around 0.6mm to 1mm, which allows room for the tooling to hold the materials together. ‘You need a bigger spot for welding, because too much power density will result in a poor join,’ Kleine said. He added: ‘Remote welding needs a fibre or disk laser, but for many welding applications direct diode will be enough.’


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