Programmable diffractive optic for multi-beam processing: applications and limitations

Gretzki, Patrick; Gillner, Arnold

doi:10.1117/12.2274448

Cited by 5 publications

(3 citation statements)

References 20 publications

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“…To increase productivity, today higher repetition rates and fluences are employed, resulting in heat accumulation and plasma shielding effects [12][13][14][15][16] . In general, heat accumulation in the machining process leads to a decrease in component quality, but Gruner et al 7 also show an increasing ablation rate in a drilling process in 100 µm thick single polished silicon, caused by the use of a higher repetition rate of 48.78 MHz at a low fluence of 0.53 J/cm².…”

Section: Introductionmentioning

confidence: 99%

Computational optimization of borehole sequences for the reduction of heat accumulation in drilling processes using ultrashort pulse lasers

Lutz,

Helm,

Esen

et al. 2024

Laser-Based Micro- And Nanoprocessing XVIII

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We report on laser drilling of borehole arrays using a high-power ultrashort pulse laser with particular focus on reducing heat accumulation in the workpiece by optimizing the drilling sequence, particularly for highly efficient multi-spot drilling. Different optimization approaches are chosen to improve the drilling sequence, also comparing a simplex algorithm and an evolutionary algorithm. From a laser application point of view, we also compare drilling sequences using a single spot and up to 16-fold multi-spots generated by a spatial light modulator, as to accelerate the drilling process in terms of the number of drilled holes per second.To evaluate the temperatures generated during drilling of up to 40,000 holes in less than 76 seconds in stainless steel foil, temperatures are measured by a thermal imaging camera and subsequently compared to a COMSOL-based simulation for all optimized drilling sequences. With respect to an average temperature of 706 °C without optimization, a reduction by 252 °C, i.e., a reduction by nearly 36 % based on the Celsius scale, is achieved using a 4 × 4 beam splitter and an optimized drilling sequence with a drilling rate of 526 holes per second. In addition, using a 2 × 2 beam splitter, a temperature reduction of up to 40.5 % is achieved for a drilling process with a rate of 129 holes per second using an optimized drilling sequence.

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Section: Introductionmentioning

confidence: 99%

Computational optimization of borehole sequences for the reduction of heat accumulation in drilling processes using ultrashort pulse lasers

Lutz,

Helm,

Esen

et al. 2024

Laser-Based Micro- And Nanoprocessing XVIII

View full text Add to dashboard Cite

show abstract

“…Aiming to increase productivity, higher repetition rates and fluences are often used, which result in heat accumulation and plasma shielding effects [12][13][14][15][16]. While heat accumulation in components generally results in negative effects in the machining process, Gruner et al [7] showed an increasing ablation rate using a high repetition rate of 48.78 MHz and a low fluence of 0.53 J/cm 2 in a drilling process in 100 µm thick single-side polished silicon.…”

Section: Introductionmentioning

confidence: 99%

Drilling Sequence Optimization Using Evolutionary Algorithms to Reduce Heat Accumulation for Femtosecond Laser Drilling with Multi-Spot Beam Profiles

Lutz,

Helm,

Tschirpke

et al. 2023

Materials

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We report on laser drilling borehole arrays using ultrashort pulsed lasers with a particular focus on reducing the inadvertent heat accumulation across the workpiece by optimizing the drilling sequence. For the optimization, evolutionary algorithms are used and their results are verified by thermal simulation using Comsol and experimentally evaluated using a thermal imaging camera. To enhance process efficiency in terms of boreholes drilled per second, multi-spot approaches are employed using a spatial light modulator. However, as higher temperatures occur across the workpiece when using simultaneous multi-spot drilling as compared to a single-spot process, a subtle spatial distribution and sequence of the multi-spot approach has to be selected in order to limit the resulting local heat input over the processing time. Different optimization approaches based on evolutionary algorithms aid to select those drilling sequences which allow for the combination of a high efficiency of multi-spot profiles, a low-generated process temperature and a high-component quality. In particular, using a 4 × 4 laser spot array allows for the drilling of 40,000 boreholes in less than 76 s (526 boreholes/s) with a reduced temperature increase by about 35%, as compared to a single spot process when employing an optimized drilling sequence.

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“…In particular, the size of the heat-affected zone, which results from a combination of laser parameters, the material properties, and the ablation process, is an important industry consideration for cutting and drilling applications using an USP laser. Aiming to increase the productivity of USP-processes, higher repetition rates and fluences are often used, which results in heat buildup and plasma shielding effects [ 12 , 13 , 14 , 15 , 16 ]. While heat accumulation generally results in negative effects, Gruner et al [ 6 ] showed an increasing ablation rate for a high repetition rate of 48.78 MHz and a low fluence of 0.52 J/(cm 2 ) during a drilling process without impairing the quality.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Heat Accumulation during Femtosecond Laser Drilling Borehole Matrices by Using a Simplex Algorithm

et al. 2022

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We report on an optimization study of percussion drilling thin metal sheets employing a high repetition rate, high power femtosecond laser with respect to the resulting heat accumulation. A specified simplex algorithm was employed to optimize the spatial drilling sequence, whereas a simplified thermal simulation using COMSOL was validated by comparing its results to the temperature measurements using an infrared camera. Optimization for drilling borehole matrices was aspired with respect to the generated temperature across the processed specimen, while the drilling strategy was altered in its spatial drilling sequence and by using multi-spot approaches generated by a spatial light modulator. As a result, we found that an optimization strategy based on limited consecutive holes in a Moore neighborhood led to reduced temperatures and the shortest process times.

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Programmable diffractive optic for multi-beam processing: applications and limitations

Cited by 5 publications

References 20 publications

Computational optimization of borehole sequences for the reduction of heat accumulation in drilling processes using ultrashort pulse lasers

Computational optimization of borehole sequences for the reduction of heat accumulation in drilling processes using ultrashort pulse lasers

Drilling Sequence Optimization Using Evolutionary Algorithms to Reduce Heat Accumulation for Femtosecond Laser Drilling with Multi-Spot Beam Profiles

Optimization of Heat Accumulation during Femtosecond Laser Drilling Borehole Matrices by Using a Simplex Algorithm

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