Greg Blackman speaks to Dr Dirk Sutter of Trumpf, who, in December last year, was presented with the 2013 German Future Prize, along with Jens Konig of Bosch and Stefan Nolte of Fraunhofer IOF, for ultrafast laser technology in operation at Bosch manufacturing plants
Last December, scientists from Bosch, Trumpf, Jena University and Fraunhofer Institute for Applied Optics and Precision Engineering (IOF) were awarded the 2013 German Future Prize for their collective effort in transforming the ultrashort-pulse laser into an effective series-production tool.
German President Joachim Gauck presented Jens König of Bosch, Dirk Sutter of Trumpf and Stefan Nolte of Fraunhofer IOF with the award, which honours top scientific work showing a high level of economic potential. The winners received €250,000 in prize money.
All three nominees for the 2013 prize were from the field of photonics – which, according to Dr Dirk Sutter of Trumpf, is in itself a big honour for the photonics industry. ‘Being finally selected by the jury was, of course, like winning an Oscar for us,’ he stated.
Bosch is using ultrafast lasers to manufacture sensors for monitoring exhaust gases in cars, as well as spray nozzles for gasoline direct injection in auto-engines. The position, form, micro-geometry and surface roughness of the holes in spray nozzles, which can measure as little as 0.1 to 0.25mm in diameter, are crucial to ensure gasoline is distributed evenly in the cylinder so that it burns completely. According to Bosch, enhanced gasoline direct injection systems can result in fuel savings of up to 20 per cent, largely through being able to machine extremely precise holes with ultrafast lasers.
Bosch drills the holes in its spray nozzles using Trumpf’s TruMicro series 5000 picosecond lasers. By 2013 about 30 million parts had been produced with ultrafast lasers, according to Bosch. ‘This is one reason why the collaboration of Bosch and Trumpf, together with universities and industrial partners, particularly with the University of Jena, won the award – the work with ultrafast lasers has resulted in processing that can really reduce CO2 emissions of vehicles. We also generated a lot of employment in Germany,’ Sutter said.
Traditionally, ultrafast lasers were laboratory tools. Sutter recalled the femtosecond systems that he worked on during his PhD, which had to be adjusted constantly to achieve the required performance. ‘When Trumpf started ultrafast laser development, vendors of scientific ultrafast lasers considered systems to be “quite reliable” if an expert “only” had to tweak them once a day. You cannot do that with a laser for industrial machining. The laser needs to basically cost nothing to run and, more importantly, have an uptime close to 100 per cent with marginal annual maintenance.’ He added: ‘For me, the biggest step was coming from one-of-a-kind lab systems to systems that were mass produced.’ Now, however, many hundreds of Trumpf’s ultrafast laser machines are being used by the major smart phone manufacturers in Asia, for example.
Sutter said that getting the uptime of the system was most crucial, which was dependent on direct diode pumping of the laser material. Trumpf uses diodes fabricated at its sister company in the US that can run constantly for at least seven years. Its ultrafast lasers employ a mode-locked fibre laser as a seed source, with low average power and high reliability of the mode-locking components using semiconductor saturable absorber mirror (SESAM) technology. These low-energy pulses are amplified in a regenerative amplifier using Trumpf’s electro-optical modulators. The company can pulse its high-voltage switches at up to a megahertz repetition rate.
Some of the machines at Bosch have been built five or more years ago and all of the lasers are still in operation, most of them running 24/7, according to Sutter.
The potential for ultrafast laser processing is enormous in many different applications, Sutter continued. For example, there are advantages to drilling fine holes in printed circuit boards with ultrafast lasers. ‘If the laser was half the price of the current systems, the hurdle [to investment] would be much lower and ultrafast lasers would be adopted much faster,’ he commented. ‘Nevertheless, now that it is possible to demonstrate the productivity and the uptime, as well as the flexibility of the laser, these benefits will probably lead to the introduction of ultrafast lasers in the mass production of printed circuit boards.’
Trumpf will present its latest TruMicro 5070 Femto Edition with sub-picosecond pulses at Photonics West, which is ideal for many machining tasks. The company, together with the University of Stuttgart, also recently reached a laboratory result of 1.3kW of average power – which, according to Sutter, is a world record.
In order to use the high average power efficiently, Sutter noted that advances need to be made in the scanner technology. Traditional galvo scanners are not fast enough to separate the pulses at megahertz repetition rate on the workpiece, he said. That means the pulse overlap is too high for cold ablation. However, there are many applications that don’t require such high average power because they work on a smaller volume, including in micro-machining.
‘I think the [ultrafast] field will widen,’ Sutter concluded. Applications for ultrafast lasers include those in display technology, electronics, photovoltaics, medical stent manufacture, laser surgery, and many others. And the fact that ultrafast lasers are now reliable enough for industrial production is credit in itself to the technology and should broaden its appeal in micro-machining.