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Process Monitoring

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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Wood Material Science

Wood Material Science & Engineering 05/2023

Supervised classification of wood species during milling based on extracted cut events from ultrasonic air-borne acoustic signals

Authors:

Mehieddine Derbas, Stephan Frömel-Frybort, Christian Laaber, Hans-Christian Möhring, Martin Riegler

Contents:
  • Monitoring during wood processing is gaining momentum in order to increase efficiency and enable adaptive manufacturing
  • Acoustic monitoring is particularly suited for the cutting/milling process
  • Derbas et al. developed a Machine Learning model to distinguish between wood species with up to 93% accuracy using single-cut events
Link

Optics and Laser Technology 04/2023

A comprehensive study on water jet guided laser micro hole drilling of an aerospace alloy

Authors:

Levent Subasi, Mustafa I. Gokler, Ulas Yaman

Contents:
  • Water-Jet Guided Laser Drilling is a process particularly suited for manufacturing of thin and long holes in metals
  • In this study, the Optical Microphone has proven to be a suitable sensor for monitoring the hole depth and the moment of hole breakthrough in real-time
Link
Inline Process Monitoring

12th International Electric Drives Production Conference (EDPC) 01/23

Inline Process Monitoring of Hairpin Welding Using Optical and Acoustic Quality Metrics

Authors:

Markus Omlor, Johannes Reith, et.al.

Contents:
  • XARION´s Optical Microphone was used to capture airborne ultrasound generated during the hairpin welding process
  • A multitude of welds were performed under varying quality-affecting parameter conditions, such as positioning misalignments or focal height and laser power deviations
  • It was found that the real-time ultrasound emission could be utilized as an early indicator for predicting the important quality criterium of final cross-sectional area of connection
Link

Proceedings of LANE 2022 Erlangen 09/2022

Monitoring of remote laser processes using air-coupled ultrasound

Authors:

R. Sommerhuber, M. Kettner

Contents:
  • XARION’s optical microphone was used for contact-free monitoring of laser processes by comparing the acoustic emissions of the process to known reference signals
  • In this paper, this monitoring method was shown to be able to detect defects and irregularities in the welding of metal sheets and of direct copper bonded substrates
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