Ultashort pulsed laser system developed to optimise machine processing
19 March 2014Tweet
Recurring lettering imprinted on a steel foil using the multi-beam scanner
Pulsar Photonics, a spin-off of the Fraunhofer Institute for Laser Technology (ILT), has developed a modified ultrashort laser system. The system uses a multi-beam approach to increase the cost effectiveness of using ultrashort pulsed techniques to process materials. The new technique allows a workpiece to be processed at 100 places at once, with the additional option to segment the laser beam. The system and multi-beam scanner will be presented for the first time to the public on 7-11 April at the Hannover Messe trade fair in Germany.
Over the past few years, the use of ultrashort pulsed lasers (USP) in material processing has been riding a wave of success. This is due to the capability to process nearly any type of material with a high degree of precision. Because the range of possible applications is continually expanding, market growth currently stands at between 20 and 25 per cent per year. Typically, the technology is used in areas such as mould technology, cutting and drilling for micro components, sieves and filters, as well as thin-film coating for solar technologies and the manufacture of OLEDs.
When it comes to micro structuring, however, today’s technology has often found itself pushed to its limits from an efficiency standpoint.
Because of these efficiency concerns, the current tool of choice for large-area surface microstructuring is the nanosecond laser – which has firmly established itself on the market thanks to impressive cost-efficiency. The drawback is that the precision of the microstructuring is limited by the accompanying melt processes; components often require extensive reworking.
By contrast, ultrashort pulsed lasers produce surface structures that do not require any further processing. They are accurate to within a few micrometers laterally and to within a hundred nanometres in depth.
However, the dominant role of evaporation in the ablation process with USP lasers means that ablation rates are around a factor of 10 lower than they are with nanosecond lasers. From a business perspective, this has often made using USP lasers to mass produce micro components seem unattractive. What is more, current USP laser systems generally cannot make use of more than 20 per cent of the available laser energy in the 50 to 100W power range.
In an effort to improve the efficiency of USP lasers in this range, researchers from Fraunhofer ILT developed a technique that allows laser ablation to run in parallel. This multi-beam technology has now been thoroughly tested and enables the laser beam to be split up into more than 100 beamlets. As a result, a workpiece can be processed at 100 places at once, which speeds up the work process accordingly. The technology means that almost all of the capacity offered by current high-performance USP laser systems can be brought to bear on the workpiece.
Pulsar Photonics has further developed the option to segment the beam. Beam segmentation essentially boosts the efficiency of workpiece processing itself; the system’s integrated measurement sensors simplify and automate both the definition of parameters during machine preparation and the monitoring of quality once the work has been completed.
As a result, the setup process takes far less time than it otherwise might. For instance, users can conduct initial machine preparation with the part already in the machine because its sensors help them to quickly determine which laser parameters will yield the best processing results. And, quality assurance is immediate because the sensors show users how deep the microstructures are, or the diameter of the holes drilled. In this way, contract manufacturers can hand the customer verified parts as soon as production is complete.
The multi-beam technology is primarily suited to the manufacture of components that feature recurring patterns and set structural arrangements, or else for working on several components with the same structure simultaneously. And in many applications, this sort of repeating structure is exactly what is required – such as the large-scale functionalisation of surfaces where the aim is to reduce friction or to produce thin-film masks and micro filters.