High-quality percussion drilling with ultrashort laser pulses

AbstractThe influence of the laser fluence on the quality of percussion-drilled holes was investigated both experimentally and by an analytical model. The study reveals that the edge quality of the drilled microholes depends on the laser fluence reaching the rear exit of the hole and changes with the number of pulses applied after breakthrough. The minimum fluence that must reach the hole’s exit in order to obtain high-quality microholes in stainless steel was experimentally found to be 2.8 times the ablation threshold.

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Model of the final borehole geometry for helical laser drilling

Advanced Optical Technologies ◽

10.1515/aot-2018-0006 ◽

2018 ◽

Vol 7 (3) ◽

pp. 183-188

Author(s):

Alexander Kroschel ◽

Andreas Michalowski ◽

Thomas Graf

Keyword(s):

Experimental Data ◽

Stainless Steel ◽

Cross Sections ◽

Ablation Threshold ◽

Laser Pulses ◽

Laser Drilling ◽

Ultrashort Laser Pulses ◽

Threshold Fluence ◽

Different Shapes ◽

Ultrashort Laser

Abstract A model for predicting the borehole geometry for laser drilling is presented based on the calculation of a surface of constant absorbed fluence. It is applicable to helical drilling of through-holes with ultrashort laser pulses. The threshold fluence describing the borehole surface is fitted for best agreement with experimental data in the form of cross-sections of through-holes of different shapes and sizes in stainless steel samples. The fitted value is similar to ablation threshold fluence values reported for laser ablation models.

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Manufacturing of high quality 3D microstructures in stainless steel with ultrashort laser pulses using different burst modes

Journal of Laser Applications ◽

10.2351/7.0000437 ◽

2021 ◽

Vol 33 (4) ◽

pp. 042002

Author(s):

Peter Lickschat ◽

Daniel Metzner ◽

Steffen Weißmantel

Keyword(s):

Stainless Steel ◽

Laser Pulses ◽

Ultrashort Laser Pulses ◽

High Quality ◽

Ultrashort Laser

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Analytical model for the depth progress of percussion drilling with ultrashort laser pulses

Applied Physics A ◽

10.1007/s00339-021-04455-3 ◽

2021 ◽

Vol 127 (5) ◽

Author(s):

Daniel Holder ◽

Rudolf Weber ◽

Thomas Graf ◽

Volkher Onuseit ◽

David Brinkmeier ◽

...

Keyword(s):

Analytical Model ◽

Experimental Validation ◽

Laser Pulses ◽

Ultrashort Laser Pulses ◽

Picosecond Pulses ◽

Hole Depth ◽

Laser Percussion Drilling ◽

Pulse Energies ◽

Ultrashort Laser ◽

Percussion Drilling

AbstractA simplified analytical model is presented that predicts the depth progress during and the final hole depth obtained by laser percussion drilling in metals with ultrashort laser pulses. The model is based on the assumption that drilled microholes exhibit a conical shape and that the absorbed fluence linearly increases with the depth of the hole. The depth progress is calculated recursively based on the depth changes induced by the successive pulses. The experimental validation confirms the model and its assumptions for percussion drilling in stainless steel with picosecond pulses and different pulse energies.

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High-quality net shape geometries from additively manufactured parts using closed-loop controlled ablation with ultrashort laser pulses

Advanced Optical Technologies ◽

10.1515/aot-2019-0065 ◽

2020 ◽

Vol 9 (1-2) ◽

pp. 101-110 ◽

Cited By ~ 1

Author(s):

Daniel Holder ◽

Artur Leis ◽

Matthias Buser ◽

Rudolf Weber ◽

Thomas Graf

Keyword(s):

Surface Roughness ◽

Closed Loop ◽

High Surface ◽

Laser Pulses ◽

Ultrashort Laser Pulses ◽

Minimum Thickness ◽

High Quality ◽

Surface Optical ◽

The Individual ◽

Ultrashort Laser

AbstractAdditively manufactured parts typically deviate to some extent from the targeted net shape and exhibit high surface roughness due to the size of the powder grains that determines the minimum thickness of the individual slices and due to partially molten powder grains adhering on the surface. Optical coherence tomography (OCT)-based measurements and closed-loop controlled ablation with ultrashort laser pulses were utilized for the precise positioning of the LPBF-generated aluminum parts and for post-processing by selective laser ablation of the excessive material. As a result, high-quality net shape geometries were achieved with surface roughness, and deviation from the targeted net shape geometry reduced by 67% and 63%, respectively.

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