Capillary depth measurement for process control

Dorsch, Friedhelm; Dubitzky, Wilrid; Effing, L.; Haug, Patrick; Hermani, Jan-Patrick; Plaßwich, Sven

doi:10.1117/12.2250108

Cited by 12 publications

(8 citation statements)

References 2 publications

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“…The laser welding of copper materials gains relevance in an increasing number of applications in electronic products such as battery tab connectors [1] and stator hairpins [2]. One crucial quality indicator for the laser welding of copper is the weld penetration depth [3,4]. Exceeding the full penetration of joint partners leads to damage to the weld joint surroundings in the product.…”

Section: Introductionmentioning

confidence: 99%

“…In consequence, experiments are performed with a changing measurement beam position in the keyhole until an optimal placement is found [1]. Such alignment is not universal and needs to be adjusted for each welding task with respect to the keyhole shape [3,17]. For instance, the higher the welding speed and the higher the laser power, the higher the distance between OCT measurement beam from the tool center point (TCP) of the processing laser, in the case of the laser welding of copper [13].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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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“…32, No. 3, 032004. https://doi.org/10.2351/7.0000086 Above all, weld penetration depth plays a key role in delivering weld quality, as discussed in [6,7,8]. For example, in the case of battery case welding, the welding process needs to be controlled to provide required weld characteristics without penetrating the battery case [9], whereas the lack of penetration in the battery tab causes an insufficient contact area, which leads to voltage drop and consequent malfunction of the whole battery pack.…”

Section: Introductionmentioning

confidence: 99%

“…In later research Kogel-Hollacher et al [17] applied a low-pass filter to compensate high frequency keyhole oscillations in welding of aluminium. Experimental results by Dorsh et al [8,18] show that the OCT measurement beam, targeting the bottom of the keyhole, has to be properly aligned with respect to the keyhole shape and that such alignment is not universal and needed to be adjusted for every specific welding task. After comparing signals from copper and aluminium alloys, Schmoeller et al [19] suggested that differences in statistical parameters of OCT signals are caused by material-dependent geometry of the keyhole, as aluminium has a tendency to form a conical geometry of the keyhole, while copper alloys show a bottle-shaped geometry that causes different reflection patterns.…”

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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“…The difference between the two light paths leads to an interference pattern and the distance data is extracted from the frequency of the occurring interference on the photo-detector [17]. Dorsch et al [18] showed that the OCT measuring beam has to be accurately positioned with respect to the bottom of the keyhole; however, finding and maintaining the alignment between the OCT measuring beam and the bottom of the keyhole is a challenging task because of the dynamic changes in the size and shape of the keyhole [19]. Those changes affect the measurement error, which in general depends upon multiple sources of variations.…”

Section: Introductionmentioning

confidence: 99%

Applying optical coherence tomography for weld depth monitoring in remote laser welding of automotive battery tab connectors

Соколов

Franciosa

Sun

et al. 2020

Journal of Laser Applications

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This paper addresses in-process monitoring of weld penetration depth (WPD) during remote laser welding of battery tab connectors using Optical Coherence Tomography (OCT). The research aims at studying the impact of welding process parameters on the accuracy of WPD measurements. In general, the highest measurement accuracy is achievable by positioning the OCT measuring beam towards the bottom of the keyhole. However, finding and maintaining the alignment between the OCT measuring beam and the bottom of the keyhole is a challenging task because of the dynamic changes in size and shape of the keyhole itself.The paper addresses the above challenge by (1) developing welding process parameters for Al-Cu thin foil lap joint (Al 1050 foil 450 μm and Ni-plated Cu foil 300 μm) using novel Adjustable Ring Mode (ARM) laser; and, (2) integrating OCT technology with two beams: one targeting the bottom of the keyhole and another as a reference to the part surface (TwinTec technology). The methodology is underpinned by the "Keyhole Mapping" approach which helps to identify the optimal placement of the OCT measuring beam with considerations to both measurement accuracy and stability of the keyhole.Findings indicated that welding with the ARM laser results in more stable process, reduces fluctuations of keyhole opening and, therefore, helps to improve the measurement accuracy by a factor of 50% (from average error of 0.22 mm to 0.11 mm). Results further identified that the feasible operating window of the OCT measuring beam, corresponding to the highest measurement accuracy, is below 20 μm in length.

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Capillary depth measurement for process control

Cited by 12 publications

References 2 publications

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

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

Applying optical coherence tomography for weld depth monitoring in remote laser welding of automotive battery tab connectors

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