Comprehensive analysis of the capillary depth in deep penetration laser welding

Fetzer, Florian; Boley, Meiko; Weber, Rudolf; Graf, Thomas

doi:10.1117/12.2250500

Cited by 12 publications

(11 citation statements)

References 9 publications

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“…17 Regarding laser beam welding, it is already known and used in macro applications to measure the keyhole depth. 18,19 Different systems are available, but are suffering with a small keyhole diameter and small weld depth occurring during laser micro welding. Furthermore, applications using galvanometer scanners for beam deflections are challenging due to chromatic aberration.…”

Section: Laser Beam Micro Welding With Spatial Power Modulationmentioning

confidence: 99%

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Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

Hollatz

Hummel

Jaklen

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part L:

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Analysing the quality of weld seams is still a challenging task. An optical inspection of the surface is giving limited information about the shape and depth of the weld seam. An application for laser beam welding with high demands regarding the weld depth consistency is the electrical contacting of battery cells. The batteries themselves have a limited terminal or case thickness that must not be penetrated during the welding process to avoid leakage or damage to the cell. That leads to a minimum weld depth to ensure the electrical functionality, and a maximum weld depth indicated by the case thickness. In such applications, a destructive analysis is not suitable which leads to the demand for a non-destructive measurement during the process. Using a coaxial, interferometric measurement setup, the keyhole depth during the deep penetration welding is measureable. For a keyhole with a depth of a couple of millimetres, such a system is commercially available. In micro scale, however, these systems are facing several challenges such as scanning systems, small spot diameters of a few tens of micrometres and narrow keyholes. This study contains an investigation of an interferometric measurement of the keyhole depth and the suitability for laser micro welding. Therefore, the data processing of the achieved measurements is investigated, and the results are compared with the depth measurement of metallographic analysed samples. Stainless steel is used to investigate the behaviour and the stability of developed data processing strategy and the resulting depth values.

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Section: Laser Beam Micro Welding With Spatial Power Modulationmentioning

confidence: 99%

“…To determine the value at a specific data point, the filter uses the values inside the range symmetrically around the actual data point. In Fetzer, 19 a moving percentile filter is used. The value range is set symmetrically around the filter value and corresponds to the measurements done in 1 ms.…”

Section: Data Processingmentioning

confidence: 99%

Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

Hollatz

Hummel

Jaklen

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part L:

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“…One solution to observe the weld penetration depth inline is optical coherence tomography (OCT). OCT is an interferometric measurement technology that enables the measurement of weld penetration depth coaxially to the processing laser in a fixed optic [5][6][7][8][9][10][11][12] or scanning optic [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Algorithms for Weld Depth Measurement in Laser Welding of Copper with Scanning Optical Coherence Tomography

Will

Garcia²,

Hoelbling³

et al. 2022

Micromachines

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In-process monitoring of weld penetration depth is possible with optical coherence tomography (OCT). The weld depth can be identified with OCT by statistical signal processing of the raw OCT signal and keyhole mapping. This approach is only applicable to stable welding processes and requires a time-consuming keyhole mapping to identify the optimal placement of a singular OCT measuring beam. In this work, we use an OCT measurement line for the identification of the weld depth. This approach shows the advantage that the calibration effort can be reduced as the measurement line requires only calibration in one dimension. As current literature focuses on weld depth measurement with a singular measurement point in the keyhole, no optimal algorithm exists for weld depth measurement with an OCT measurement line. We developed seven different weld depth processing pipelines and tested these algorithms under different weld conditions, such as stable deep penetration welding, unstable deep penetration welding, and heat conduction welding. We analyzed the accuracy of the weld depth processing algorithms by comparing the measured weld depth with metallographic weld depths. The intensity accumulation approach is identified as the most accurate algorithm for successful weld depth measurement with a scanning OCT measurement line.

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“…Comparing OCT signals during laser welding of mild steel and aluminium alloy, Bautze et al [7] noticed that in case of aluminium, the signal has a wider variance and proposed that the signal's variance can be used to determine the process window. Comparing OCT sensor signal with X-ray, Fetzer et al [15] used 80th percentile filter with a 1.0 ms symmetrically placed window as it resulted in a minimal deviation between the depth measured with both methods. Kogel-Hollacher et al [16] used two measurement beams ("TwinTec" module): one towards the keyhole and the second focused on the base material surface to get the precise weld penetration depth value as a result of subtraction of these two signals.…”

Section: Introductionmentioning

confidence: 99%

Keyhole mapping to enable closed-loop weld penetration depth control for remote laser welding of aluminum components using optical coherence tomography

Соколов

Franciosa

Botros

et al. 2020

Journal of Laser Applications

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Remote laser welding (RLW) combines the positive features of tactile laser welding with additional benefits such as increased processing speed, reduced operational cost and service, and higher process flexibility. A leading challenge preventing the full uptake of RLW technology in industry is the lack of efficient closed loop in-process (CLIP) monitoring and weld quality control solutions. This underpins the need to fuse multiple sensor technologies and data analytics with predictive engineering simulations. Although the development and integration of a variety of sensors covers the radiation spectrum from ultraviolet to farinfrared, the flawless deployment of CLIP solutions is still challenged by the need for the following: signal denoising in the case of process instability; real-time data analytics; and adaptive control engineering architecture to cope with process variations induced by manufacturing tolerances. This paper focuses on the aspect of weld penetration depth control using optical coherence tomography (OCT) as a necessary step to enable adaptive penetration depth control during RLW of aluminum components in the fillet lap joint configuration with consideration to part-to-part gap variation. The approach entails decoupling the welding process parameters in two subsets: (1) in-plane control of the heat input on the upper part to facilitate the droplet formation; and (2) out-of-plane heat management to achieve the desired level of penetration control in the keyhole mode. This paper presents the results of finding the optimal placement of the OCT beam with variable part-to-part gap conditions. Results have shown that statistical signal processing of the raw OCT signal gives insight not only into the depth of the keyhole but can infer the shape of the keyhole itself. Current limitations and next phases of research and development are highlighted based on the experimental study.

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Comprehensive analysis of the capillary depth in deep penetration laser welding

Cited by 12 publications

References 9 publications

Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

Algorithms for Weld Depth Measurement in Laser Welding of Copper with Scanning Optical Coherence Tomography

Keyhole mapping to enable closed-loop weld penetration depth control for remote laser welding of aluminum components using optical coherence tomography

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