Junior research scientists honored for ultrashort laser pulses
Bosch research scientists can machine components to even greater levels of precision with ultrashort laser pulses. This enables engineers in the automotive field to reduce pollutant emissions and fuel consumption even further.
A small bluish cloud of steam, perhaps the size of a pin head, is all that can be seen. The laser has then done its job. No hissing, no flying sparks. The component now held in Jens König's hands is a minute structure richer: In a matter of seconds the laser has carved into an injection component a groove just 10 micrometers (thousandths of a millimeter) wide.
The achievement of König and his colleagues Thorsten Bauer, Markus Willert and Ulrich Graf in developing a laser technology for these filigree microstructures and in adapting this technology to manufacturing processes with cycle times of a few seconds earned them the 20,000-euro innovation prize of the Berthold-Leibinger Foundation. This prize is one of the most internationally respected and rich awards in the field of laser technology.
... to series production
In his laboratory in the Bosch Research and Development Center in Schwieberdingen Jens König escorts visitors through a small labyrinth of gray cabinets and distributed monitors. The cabinets house control electronics and cooling technology for the machining system and the ultrashort-pulse laser. When he then slides one side of a cabinet upwards and points to the complicated arrangement of mirrors on the optical bench, he goes into raptures. The complicated laser system which he and his colleagues have assembled in meticulously detailed work is capable of incorporating microscopically small structures quickly and precisely into many different materials. "We can structure, trim, bore and cut with the laser light," explains König. The dimensions are usually within a range of just a few micrometers.
His colleague Thorsten Bauer uses the ultrashort-pulse laser in the first pilot application in the Bamberg production plant. There, specific components in the engine's exhaust-management system can be tweaked to particularly high levels of precision and efficiency with the laser. This enables the product design engineers to optimize the exhaust-emission values.
Laser flashes vaporize the material
Further applications, such as the aforementioned groove for example, are to follow soon. The cheap manufacture of such filigree cuts in the base material has until now been wishful thinking on the part of engineers. "Only with the ultrashort-pulse laser can this be achieved," says König. With pulse durations of picoseconds (10 -12seconds) the laser fires several hundred thousand times at the surface within the process time of a few seconds. The result is a clean groove, with no melting burs or thermal deformations of the material.
The trick to the process lies in the fact that the physicists at Bosch deposit the light energy into the material surface with the laser beam in the extremely short periods of time. First the electrons absorb this energy, then they heat up to in excess of 10,000 °C, expand and take with them the neutral atoms from the molecular lattice of a metal or from the molecular structure of a plastic. "At these high intensities every material collapses," says König. All common materials, metals, semiconductors, ceramics, glass and plastics can be machined with an accuracy of a few micrometers.
Joint project lays the foundations
In order to apply the maximum output of over 100 megawatts quickly and precisely to the respective component, Jens König and his research colleague Markus Willert had to come up with some ideas and immerse themselves wholeheartedly into the fundamentals of physics. In a joint project supported by the Federal Ministry for Education and Research the two have elaborated these fundamentals together with partners from universities and from industry. Starting out from this physical understanding of the interaction between light and matter as well as the removal processes which take place in these incredibly short timescales, they were able to specify suitable laser parameters. These were realized by the company Trumpf in several function specimens and tested in the laboratories at Bosch. In this way, the team around Jens König was able step by step to work out the best laser parameters for the systems and process engineering utilized.
Relentless production cycle
However, what is innovative for König is not necessarily the laser technology used, which he has developed further in conjunction with the world market leader Trumpf. He sees the innovation rather in his specific know-how of having adapted the system to fit the framework conditions of a production line for large-scale production. "Every leading laser-research institute is familiar with and applies this laser technology," says König. But it takes these institutes considerably longer to machine to such levels of precision. "And we manage this in a few seconds," explains König. But he will not go into specific details, such as laser focusing, scanning rate and pulse rate. "This is where we have our competitive knowledge-based edge," he says with a wink.
Research scientist König: "Good opportunities to make progress with something"
At 32 years of age, König is almost an old hand in his department already: Six years ago the Würzburg-born König, after completing his physics studies at Würzburg University, arrived at the high-tech group to do his doctorate in the physical removal processes when machining with ultrashort-pulse lasers. "I had applied directly to Research on the internet," he says. After barely a week he had been accepted for his doctorate post. You can now see that looking back on the past few years makes him happy: "Here in Research there have always been very good opportunities to make progress with something. While I was doing my doctorate I was able to focus entirely on research. Since then, what I appreciate in particular is the fact that I can decide how I approach things technically. I have always appreciated and used this freedom." Now König and his team are applying their development, in other words: to large-scale series production in the plants. The young father then intends to devote himself to new tasks.
