The paper discusses results obtained in ultrashort pulselaser irradiation of metals in order to characteriseinteraction phenomena occurring in highly repetitivelaser processing, such as heat accumulation andparticle shielding. The impact of the temporal pulse-topulsedistance on the ablation process was investigatedusing repetition rates ranging between 25.8 kHz and2.05 MHz. Interacting effects were studied by meansof industrial grade metal sheets with various thermophysicalcharacteristics. The experimental resultsobtained were evaluated by theoretical calculations ofboth the ablation rate and surface temperature.Furthermore ultra high speed camera images weretaken into discussion.Ablation rates obtained empirically for stainless steeland aluminium indicate increasing material removal athigher repetition rates and, hence, heat accumulation isproven as influencing effect. Thus in case of stainlesssteel and shorter pulse-to-pulse distances, temperaturecalculation yields the rise of the surface temperature.Additionally, ultra high speed camera images giveevidence of more voluminous ablation plumes atshorter pulse-to-pulse distances, induced by intenselaser matter interaction.In contrast, for copper only a marginal impact of therepetition rate on the material removal was found.Thus for highly heat-conductive materials the ablationrate is assumed almost independent from the temporalpulse-to-pulse distance. Even high speed cameraimages show minor impact of the repetition rate on theablation process.Finally the application of the laser micro machiningtechnology in micro-mould manufacturing ispresented. As a result micro-featured plasticdemonstrators were produced by micro injectionmoulding, offering a wide range of sensor applications,for example in microfluidic systems.
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