Advances of OCT Technology for Laser Beam Processing

Dupriez, Nataliya Deyneka; Denkl, Alexander

doi:10.1002/latj.201700021

Cited by 21 publications

(6 citation statements)

References 7 publications

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“…OCT is an interferometric measurement technology that enables the assessment of the welding bead by non-destructive distance measurement [3][4][5][6][7]. OCT can be applied to identify misalignments in pre-process Faculty 1 (Physics/Electrical Engineering), University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany monitoring, the weld depth in in-process monitoring, and the shape of the resulting weld in the post-process monitoring stage [8,9]. Baader et al [8] analyzed the potential of OCT for process monitoring of laser welding hairpin windings.…”

Section: Introductionmentioning

confidence: 99%

Prediction of electrical resistance of laser-welded copper pin-pairs with surface topographical information from inline post-process observation by optical coherence tomography

Will

Müller

Müller³

et al. 2023

Int J Adv Manuf Technol

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Laser welding of copper hairpins is required to produce a conductive connection in electric stators. Past manufacturing processes introduce misalignments that lead to poor weld connections with increased electrical resistance. In this work, we discuss correlations between the electrical resistance of the weld connection and possible misalignment types. Misalignments lead to a deformed surface topography of the weld. We correlate inline measurements of the weld topography by optical coherence tomography (OCT) with misalignment types and hence erroneous weld connections. We identify a connection between surface topographical weld features with the electrical resistance of the weld. As a result, a quantified separation of process results is possible with a surface topographical feature of the hairpins that allows for concluding the electrical resistance of the pin-pair connection. Correlation coefficient is identified as the most relevant feature indicating a linear trend in the height profile. Reference measurements with a symmetrical weld pearl show a correlation coefficient of around 0, whereas misalignments with a skewed surface topography show increased absolute correlation coefficient values up to 0.75. The identified correlation between the electrical resistance and different misalignment types can be depicted with the correlation coefficient for the given boundary conditions. Defective weld results with electrical resistances above 6 µΩ can be identified with feature values above 0.5, whereas reference welds with an electrical resistance below 5 µΩ can be identified with an absolute correlation coefficient below 0.2.

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Section: Introductionmentioning

confidence: 99%

Prediction of electrical resistance of laser-welded copper pin-pairs with surface topographical information from inline post-process observation by optical coherence tomography

Will

Müller

Müller³

et al. 2023

Int J Adv Manuf Technol

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“…For industrial applications, OCT is emerging as an important tool to ensure quality control in laser weld systems, as any changes in the laser weld process parameters can affect the size or the mechanical behavior of welded joints, thereby resulting in possible risk of early wear-out, fatigue or component failure [5,6,7]. Similarly, for laser metal deposition (LMD) in 3D printing or other applications, advanced imaging systems are integrating OCT to monitor and stabilize the deposition process [8].…”

Section: Introductionmentioning

confidence: 99%

Integrated 840nm high-power dual-polarization SLED source

Gloor¹,

Ríos²,

Primerov³

et al. 2023

Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXVII

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We demonstrate, to our knowledge for the first time, an integrated light source module that emits broadband amplified spontaneous emission (ASE) light from two superluminescent diodes (SLEDs) through a single-mode fiber output simultaneously on two orthogonal polarizations. The dual-polarization SLED source is realized on a free-space, temperature-stabilized, micro-optical bench and integrated in a 14-pin butterfly module. The broadband light output from the single-mode fiber has twice the output power of a single-SLED source and achieves a polarization extinction ratio (PER) of 0 dB when the relative power levels of both SLED sources are carefully balanced.

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“…Recent advances have shown the possibility to use OCT for preprocess, inprocess, and postprocess monitoring and control by its insusceptibility to other optical distortions. [9][10][11][12] Sokolov et al 13 researched OCT sensors for RLW to enable a closed-loop control for the gap-to-gap bridging of aluminum plates. Their work confirmed the use of the OCT sensor to control and measure weld penetration depth.…”

Section: Introductionmentioning

confidence: 99%

Fusing optical coherence tomography and photodiodes for diagnosis of weld features during remote laser welding of copper-to-aluminum

Brežan

Franciosa

Jezeršek

et al. 2023

Journal of Laser Applications

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This study has been designed to investigate whether variations in the features of laser weldments can be isolated and diagnosed by fusing photodiodes and optical coherence tomography (OCT). Two manufacturing scenarios (variation in laser power and focal offset) have been considered during remote laser welding of 0.2 mm thick Cu foils on 2 mm thick Al 1050 plates with an adjustable ring mode laser integrated with a 1D oscillation head. The process was monitored by measuring weld penetration depth with OCT and by process emissions (plasma and back-reflection) via photodiodes. The acquisition frequency of all signals was 40 kHz. Strong correlations (r > 0.75) were shown between plasma, back-reflection, and OCT signals and measured depth and width of the weld. Weak correlations (r < 0.5) between voids, cracks, and sensor signals were observed. Although plasma is the predominant signal that carries most of the information about the process, and the OCT allows direct measurement of the penetration depth, their integration reached 87% classification accuracy of the tested welding scenarios. The main misclassification was observed between “good weld” and “over weld,” defined by the measured weld depth. Sensor fusion strategies with manufacturing implications are discussed throughout the paper.

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Advances of OCT Technology for Laser Beam Processing

Cited by 21 publications

References 7 publications

Prediction of electrical resistance of laser-welded copper pin-pairs with surface topographical information from inline post-process observation by optical coherence tomography

Prediction of electrical resistance of laser-welded copper pin-pairs with surface topographical information from inline post-process observation by optical coherence tomography

Integrated 840nm high-power dual-polarization SLED source

Fusing optical coherence tomography and photodiodes for diagnosis of weld features during remote laser welding of copper-to-aluminum

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