Aachen, Germany - Plant manufacturers and end users of laser processing typically aim to optimize the manufacturing processes regarding precision, reliability, and the involved time, material, and costs. To do this, they need exact information of process-relevant variables from which they can derive concrete measures. Especially with laser manufacturing processes, important process variables can be measured only poorly or not at all in the few micrometers of the process zone due to the small dimensions or the very high temperatures.
To optimize laser processes, engineers are employing computer simulations more and more often. These enable them to "look into" the process and – in comparison to experiments – simulations can be more easily automated and more cost-efficient. Moreover, in such simulations, deviations and measurement inaccuracies can not only be excluded, but also be specifically taken into account. This way, key positions can be found and problems recognized early and solved.
For about 20 years, a 12-member team of highly specialized scientists at the Fraunhofer ILT has been working solely on the computer-supported simulation of laser processes. At their disposal is a high-performance cluster of computers, which was set up on the Fraunhofer premises within the scope of the "Center for Nanophotonics" in 2010. This way, the experts in Aachen can simulate complex questions from laser material processing with high resolution in the briefest computing time and derive concrete approaches to solutions from this information. When lasers are used to cut display glass, for example, simulation of the processes can both increase the ablation speed as well as prevent damage to the glass.
Because of the findings from the simulations, ILT experts can contribute significantly to the product and process development of their industrial partners. At the LASER World of Photonics in Munich, they will be presenting five examples of this kind of successful cooperation.
Among these are:
- cutting display glass with ultra-short pulse lasers for TRUMPF Laser Technology,
- water-guided laser cutting for SYNOVA,
- optimization of metal cutting for TRUMPF Machine
- optimize laser beam sources for ROFIN-SINAR and
- free-form lens prototypes were calculated for the automotive supplier HELLA.
Ultra-short pulse laser systems are achieving new records almost daily regarding laser power and pulse rates. And yet in the power range of 50 to 1000 W, only a small part of the energy can be used effectively for many applications. If the laser power is too high when it is coupled into the workpiece at the processing point, bulges from the melting effects occur due to the high thermal load, leading to poor processing results.
Now, the research work at the Fraunhofer ILT is looking at making the high power of USP lasers useful for material processing, for example, by dividing the laser beam into several individual beams, which then can process the component simultaneously. This multi-beam technique is used, among others, to generate periodic microstructures.
A further approach to using the high laser power exists in guiding the laser at high speeds. To achieve this, ILT scientists have developed a polygon scanner system. In it, a polygon mirror rotates at a high, constant revolution and guides the beam along a line on the workpiece. As the laser beam is guided along this line at the speed of sound, the high laser power is distributed evenly along the work piece. An axis perpendicular to this line moves the workpiece so that the area to be processed is clamped. This scanning technology is particularly suitable for processing surfaces since the workpiece is processed in lines. The polygon scanner system can be employed, in particular, for the structuring of printing and coining plates, as well as injection molds, for the generation of light guiding structures in the lighting industry or for leather grain structures in the automobile and textile industries.
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