High-rate laser processing for high-precision surface profiling and functionalizationWednesday (24.06.2020) 18:00 - 18:20 Room 3
High-rate laser machining using both ultrashort pulse and continuous wave lasers of kilowatt output powers in combination with ultrafast laser beam movements will be introduced as key technology for advanced surface processing and functionalization. In fact, the polygon-mirror based scan technique developed for raster-scanning the laser beam at unprecedented speeds is the core feature to bring such high optical powers from the laboratory to industrial production. This is particularly suitable for power scaling in micro machining as processing rate and throughput scale-up with both higher pulse repetition frequency and laser power. The great advantage of the ultrafast beam movements in the range of hundreds of meters per second and above is that unfavourable effects as observed for high-power lasers in materials processing can easily be avoided, such as high thermal loads to the substrates and subsequent material melting as well as laser beam shielding by its interactions with the previously induced plasma/particle plume.
The first part of this talk on high-rate laser processing deals with how the laser parameter settings influence the achievable removal efficiency, processing speed, throughput and machining quality. In addition, new insights on the effects of ablation-cooling and beam shielding will be presented, providing valuable information for using high-power lasers in micro machining. In the second part, the high potential of flexible and high-precision laser machining for advanced surface engineering will be discussed by the example of riblet profiles, see Figure 1. Inspired by sharks´ skin, the laser made riblets were chosen as demonstrator because of their effectiveness for drag reduction in turbulent flows. For the riblets produced on a test cylinder, a drag reduction of -6.3 % was measured under well-defined test conditions that is slightly less than the theoretical estimate of -7.0 % for ideal trapezoidal riblets. This drag reducing effect as confirmed for the laser made riblet along with the high processing rates that can be achieved with the high-rate laser technology attracts high-precision laser profiling for innovative industrial applications in the energy machinery sector.
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