Inline measurement for quality control from macro to micro laser applications (Conference Presentation)

Kogel‐Hollacher, Markus; Schoenleber, Martin; Schulze, J.; Bautze, Thibault; Strebel, Matthias; Moser, Rüdiger

doi:10.1117/12.2249676

Cited by 3 publications

(4 citation statements)

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“…While these disturbances can be reduced, for example, through the use of customized laser intensity profiles, 4 they cannot be completely suppressed. Therefore, different approaches for data filtering and extracting the keyhole bottom position from raw data have been established, such as percentile 5 or Kalman 6 filters. When calibrated, these filters can reliably estimate the actual welding depth with good alignment with the respective metallographic sections.…”

Section: Understanding the Coaxial Optical Coherence Tomography Signa...mentioning

confidence: 99%

Understanding the coaxial optical coherence tomography signal during the laser welding of hidden T-joints

Mattulat

2023

Journal of Laser Applications

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In the case of “hidden” T-joints, the nonvisible web sheet is welded through the face sheet. Positioning tolerances and movement due to the distortion of the web sheet represent the main challenges to maintain on track during laser beam welding. This study investigated the assumption that keyhole monitoring based on optical coherence tomography (OCT) could be utilized for seam tracking by detecting critical misalignments between the laser beam and the web sheet position. It hereby analyzed whether an emerging misalignment between the laser beam and the web sheet could be discerned in the OCT data before the laser beam misses the web sheet and penetrated only the face sheet. This prediction represents a key requirement for the industrial use of this approach. To this end, this study investigated the welding of hidden T-joints with angular and parallel offsets of the laser path relative to the web sheet centerline while recording with OCT. The interface zone between the web and face sheets was recorded by a high-speed camera to detect the transmission of laser radiation through a lower keyhole opening. It was shown that a lower keyhole opening, in combination with transmitted radiation, was advantageous for the reliable detection of an emerging misalignment. This lower keyhole opening can occur lateral to the web sheet prior to a misalignment, therefore enabling a prediction of spot misalignments via OCT. The welding parameter dependent maximum distance of the laser spot edge to the web sheet edge at detection was 0.1 mm in this study.

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Section: Understanding the Coaxial Optical Coherence Tomography Signa...mentioning

confidence: 99%

Understanding the coaxial optical coherence tomography signal during the laser welding of hidden T-joints

Mattulat

2023

Journal of Laser Applications

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“…For the inline evaluation of the weld depth during deep penetration welding, the OCT sensor signal allows for direct conclusions about the stability of the welding process [7]. Schmoeller et al [8], Kogel-Hollacher et al [9], Sokolov et al [10] and Webster et al [11] demonstrated the applicability of an OCT-based sensor for the measurement of the keyhole depth, the keyhole position mapping in micro laser beam welding and the 3D surface measurement in remote laser ablation, respectively. Fundamental insights regarding the relationship between the keyhole geometry in laser beam welding and the signal from OCT-based keyhole depth measurements were presented by Stadter et al [12].…”

Section: Inline Weld Depth Measurement For Deep Penetration Laser Bea...mentioning

confidence: 99%

Inline Weld Depth Evaluation and Control Based on OCT Keyhole Depth Measurement and Fuzzy Control

et al. 2022

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In an industrial joining process, exemplified by deep penetration laser beam welding, ensuring a high quality of welds requires a great effort. The quality cannot be fully established by testing, but can only be produced. The fundamental requirements for a high weld seam quality in laser beam welding are therefore already laid in the process, which makes the use of control systems essential in fully automated production. With the aid of process monitoring systems that can supply data inline to a production process, the foundation is laid for the efficient and cycle-time-neutral control of welding processes. In particular, if novel, direct measurement methods, such as Optical Coherence Tomography, are used for the acquisition of direct geometric quantities, e.g., the weld penetration depth, a significant control potential can be exploited. In this work, an inline weld depth control system based on an OCT keyhole depth measurement is presented. The system is capable of automatically executing an inline control of the deep penetration welding process based only on a specified target weld depth. The performance of the control system was demonstrated on various aluminum alloys and for different penetration depths. In addition, the ability of the control to respond to unforeseen external disturbances was tested. Within the scope of this work, it was thus possible to provide an outlook on future developments in the field of laser welding technology, which could develop in the direction of an intuitive manufacturing process. This objective should be accomplished through the use of intelligent algorithms and innovative measurement technology—following the example of laser beam cutting, where the processing systems themselves have been provided with the ability to select suitable process parameters for several years now.

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“…SD-OCT has significant advantages of imaging speed and sensitivity and can be applied to nonmedical applications [6,7]. In recent years, it showed promise in laser materials processing such as laser drilling [8], laser additive manufacturing [9][10][11] and laser welding [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

“…Kogel-Hollacher et al also developed a measuring system based on SD-OCT to monitoring the keyhole depth. Via feeding the laser source with a control signal determined by the measured keyhole depth, closed-loop control of the welding depth was achieved [15].…”

Section: Introductionmentioning

confidence: 99%

An Efficient Method for Laser Welding Depth Determination Using Optical Coherence Tomography

Xie

Wang²,

Zhang

et al. 2023

Sensors

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Online monitoring of laser welding depth is increasingly important, with the growing demand for the precise welding depth in the field of power battery manufacturing for new energy vehicles. The indirect methods of welding depth measurement based on optical radiation, visual image and acoustic signals in the process zone have low accuracy in the continuous monitoring. Optical coherence tomography (OCT) provides a direct welding depth measurement during laser welding and shows high achievable accuracy in continuous monitoring. Statistical evaluation approach accurately extracts the welding depth from OCT data but suffers from complexity in noise removal. In this paper, an efficient method coupled DBSCAN (Density-Based Spatial Clustering of Application with Noise) and percentile filter for laser welding depth determination was proposed. The noise of the OCT data were viewed as outliers and detected by DBSCAN. After eliminating the noise, the percentile filter was used to extract the welding depth. By comparing the welding depth determined by this approach and the actual weld depth of longitudinal cross section, an average error of less than 5% was obtained. The precise laser welding depth can be efficiently achieved by the method.

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Inline measurement for quality control from macro to micro laser applications (Conference Presentation)

Cited by 3 publications

References 0 publications

Understanding the coaxial optical coherence tomography signal during the laser welding of hidden T-joints

Understanding the coaxial optical coherence tomography signal during the laser welding of hidden T-joints

Inline Weld Depth Evaluation and Control Based on OCT Keyhole Depth Measurement and Fuzzy Control

An Efficient Method for Laser Welding Depth Determination Using Optical Coherence Tomography

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