Processing of metal

Femtosecond lasers enable the production of complex shapes and features, while also providing the capability to perform black/white marking and coloring without the need for chemical additives.

Metal

MHz burst usage in increasing femtosecond removal efficiency in aluminum, copper and stainless steel

Femtosecond processing of materials faces a significant challenge in terms of process throughput. There exists an optimal fluence value at which the most efficient material removal occurs. However, with high average power lasers, achieving this optimal fluence is difficult. In order to achieve the optimal fluence at higher powers, one is forced to increase the repetition rate to values where significant thermal accumulation occurs, often leading to degradation in processing quality. The optimal fluence can be achieved by using MHz burst mode, which splits the high-energy pulse into multiple sub-pulses, enhancing the efficiency of material processing, especially metals, compared to single-pulse mode.

In a recent study by A. Žemaitis et al., the FemtoLux 30 laser was used to optimize machining methods for aluminum, copper, and stainless steel. The researchers conducted material removal optimization by milling 110 cavities in a single metal sample, varying the pulse repetition rate and the number of pulses in the burst. Utilizing MHz burst mode allowed to achieve optimal fluences, resulting in not only high removal efficiency but also great surface roughness. Especially, removal efficiency and rate were increased by 18%, 44.5% and 37% for aluminum, copper and stainless steel accordingly, if compared to the single-pulse operation mode.

Efficiently laser milled aluminium Fresnel lens mould diameter 35 mm.

Efficiently laser milled aluminium Fresnel lens mould, diameter 35 mm: (a) optical photograph, (b) 3D height map and (c) 2D profile from the middle of the structure.

Courtesy of FTMC.

Results of processing various metal samples with MHz burst

MaterialRemoval efficiencyRemoval rateSurface roughnessNo. of pulses in burst
Aluminum7.0 µm3/µJ9.2 mm3/min1.7 µm10
Copper4.2 µm3/µJ5.6 mm3/min2 µm5
Steel3.9 µm3/µJ5.1 mm3/min1.7 µm10
MaterialRemoval efficiencyRemoval rateSurface roughnessNo. of pulses in burst

The ultrafast burst laser ablation of metals: Speed and quality come together

A. Žemaitis, U. Gudauskytė, S. Steponavičiūtė, P. Gečys, and M. Gedvilas, Optics & Laser Technology 180, 111458 (2024). DOI: 10.1016/j.optlastec.2024.111458.

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