The photonics industry is currently undergoing a transition to a third generation of laser cutting technology, attendees to the AILU Industrial Laser Applications Symposium were told. The event took place 22-23 March in Grantham, UK.
According to Gaetano Lo Guzzo, director of European laser business at Yamazaki Mazak, a Japanese machine tool builder, direct diode lasers are the future of laser cutting and have already begun taking over from fibre lasers, starting in 2016.
Lo Guzzo expressed that while diode technology itself is not new for cutting, after a lot of time and experimentation, wavelength combiners are now being used to convert multiple diode wavelengths into very high energy density, high quality beams. According to Lo Guzzo, these wavelength-combining diode lasers systems are a ‘revolution’ for laser users; however, they still have a lot of room to grow.
Lo Guzzo explained in his talk that diode lasers provide numerous advantages over fibre lasers when it comes to cutting, namely a higher energy efficiency, faster cutting speeds, higher quality cutting edges and a lower cost of ownership – up to 20 per cent less, he said.
In terms of energy efficiency, Lo Guzzo remarked that a 1,070nm fibre laser offers a 40 per cent conversion rate, while direct diode lasers at 975nm offer 50 per cent. In addition, this small reduction in wavelength increases the absorption of the laser in certain materials, such as mild and stainless steels, leading to cutting speeds that are up to 20 per cent faster.
However, other commentators have said that fibre lasers are still the best solution for metal cutting. Commenting in an article for Laser Systems Europe, Coherent’s product line manager, Klaus Kleine, said: ‘Diode laser systems made for very high brightness applications less than 20mm-mrad look very complex to me,' adding 'I believe that the best brightness converter is still the fibre laser. The fibre laser seems to be the more elegant solution for now. I expect that to change, but it will take time.’
Lo Guzzo said that Yamazaki Mazak will release powers higher than 4kW for its direct diode machines in the near future. In addition to this, 400nm direct diode lasers - yet to be developed - could lead to a range of new applications. ‘We believe that the direct diode laser generation for high power will have a lot of potential applications in the coming years,’ Lo Guzzo confirmed.
Currently, the highest thickness of mild steel that has been cut using a direct diode laser is 22mm, while the thickest stainless steel has been 17.5mm. Lo Guzzo also stated in his presentation that, for 1mm-thick aluminium, direct diode lasers offer double the cutting speed of fibre lasers.
In comparison to CO2 lasers, which, according to Lo Guzzo, are still used in industry because of the high beam and cutting quality they offer, direct diode lasers are able to provide a higher beam quality, shorter wavelengths and up to five times higher efficiency.
Diode lasers currently hold a 25 per cent share in the global market for laser sources for materials processing – sources used in cutting, welding, marking, and additive manufacturing – while fibre lasers remain ahead with a 40 per cent share, according to market research firm Optech Consulting. CO2 and excimer sources account for a 35 per cent share in the market, which, according to the firm, grew 15 per cent last year to $1.3 billion.
Diode lasers are as tough and durable as fibre lasers, Lo Guzzo said in his presentation, while providing higher feed rates, lower gas usage, higher running times and lower labour costs. Their design also leaves room to improve their quality, which could lead to them being adopted for an even wider range of applications.
The direct approach - Greg Blackman investigates the advances being made in direct diode lasers and asks whether these systems can compete with fibre lasers