Publications

Journal of Laser Applications  03/2025

Layer detection in ultrashort pulsed multilayer laser ablation by analyzing ultrasonic process emission

Authors:

Christian Lutz, Cemal Esen, Ralf Hellmann

Contents:

• Laser ablation is used for processing electronic applications (e.g. PCB)
• This paper presents the detection of material transitions during laser ablation by analyzing acoustic data captured with an optical microphone.
• The focus of this work was on the material transition between polyimide and copper. Due to the higher removal rate in polyimide compared to copper, a    significant increase in acoustic energy was detected at the material transition.
•  In addition to detecting material transitions, a correlation between the emitted acoustic energy and layer thickness was observed.

Link

17th CIRP Conference on Intelligent Computation in Manufacturing Engineering (CIRP ICME ‘23)  08/2024

In-situ acoustic signals correlation of process parameters in laser powder bed fusion

Authors:

Levent Subasi, Soner Oren, Gokhan Dursun, Cagdas Sen, Akin Orhangul

Contents:

• Laser powder bed fusion (LPBF) is a metal additive manufacturing technique in which repeatability is a major concern in quality results.
•          An optical microphone was used to monitor the acoustic emission during the LPBF process.
•          The analysis showed a strong correlation between the acoustic signals and the process parameters.
•         This methodology allows for the evaluation of process flaws and overall quality.

Link

Applied Sciences 10/2024

Acoustic Emission and Digital Image Correlation-Based Study for Early Damage Identification in Sandwich Structures

Authors:

Aitor García de la Yedra, Igor Erro, et al.

Contents:

• Monitoring the quality of complex sandwich structures is difficult with common testing techniques for accessibility reasons
• A novel approach to solve this issue is enabled by acoustic monitoring in the ultrasound regime with the Optical Microphone
• The results from acoustic monitoring were compared to findings obtained with digital image correlation
• It could be shown that early identification of structural damage is possible with the Optical Microphone

Link

Additive Manufacturing 01/2024

Healing of keyhole porosity by means of defocused laser beam remelting: Operando observation by X-ray imaging and acoustic emission-based detection

Authors:

Charlotte de Formanoir, Milad Hamidi Nasab, et al.

Contents:

• In Laser Powder-Bed Fusion (LPBF) the unpredictable formation of defects such as pores can lead to compromised mechanical properties
• Using XARION’s optical microphone a strategy for monitoring in-situ healing of pores through laser remelting was implemented
• Acoustic signals acquired during laser remelting are temporally synchronized and analyzed with X-ray images to identify acoustic signatures of the pore healing event
• The approach presented in this paper enables precise monitoring of defect healing during the LPBF process without the use of elaborate machine learning algorithms

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SPIE. Photonics West 01/2024

Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials

Authors:

C. Lutz, R. Sommerhuber, M. Kettner, C. Esen, R. Hellmann

Contents:

• Ultra-short-pulsed laser ablation of thin multilayer materials can be monitored using XARION’s Eta450 Ultra optical microphone
• It is possible to monitor the material transition between polymer and copper during laser ablation by observing a broad acoustic frequency spectrum between 100 kHz and 2 MHz in air, and by detecting a sudden change in acoustic energy
• A direct correlation was found between increased detected acoustic energy and higher ablation rate

Link

Nature Communications 12/2023

Harmonizing sound and light: X-ray imaging unveils acoustic signatures of stochastic inter-regime instabilities during laser melting

Authors:

Milad Hamidi Nasab, Giulio Masinelli, et al.

Contents:

• Laser Powder Bed Fusion Additive Manufacturing (LPBF AM) is a metal additive manufacturing process capable of directly producing intricate three-dimensional metallic components from CAD models
• The present work deploys high-speed synchrotron X-ray imaging to scrutinize keyhole melting instabilities in LPBF and correlates these with the process’ acoustic emission (AE)
• XARION’s optical microphone was used to measure airborne AE from the interaction zone between laser and material
• The transition between conduction, stable keyhole, and unstable keyhole regimes, which leads to porosity formation and other instabilities, can successfully be discerned using the AE data

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