Low-coherence interferometry in laser processing: a new sensor approach heading for industrial applications

Kogel‐Hollacher, Markus; André, Stephan; Beck, Tobias

doi:10.1117/12.2501295

Cited by 8 publications

(4 citation statements)

References 7 publications

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“…In this context we talk about monitoring systems based on photo diode technology [3], evaluating quality based on the emissions emerging from the interaction zone. We also talk about the adaptation of OCT sensor technology [4] [5][6] [7][8] [9] to the processing tools being able to perform real measurements in physical units deriving a go/no go message. Within laser material processing, this sensor technology came into focus about 10 years ago.…”

Section: Photonics In the Field Of Battery-powered Vehiclesmentioning

confidence: 99%

Meeting the challenges in e-mobility with laser welding and sophisticated system technology

Kogel-Hollacher,

Reiser,

Nicolay

et al. 2024

Laser-Based Micro- And Nanoprocessing XVIII

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It is becoming increasingly clear that there is more than just a gradual change in the automotive industry, especially when it comes to future drive systems. There are different designs and degrees of electrification -from hybrid to pure battery vehicles -with different electrical outputs, ranges and driving shares. New components significantly change the share of value added in the vehicle. The focus of value creation is shifting further from mechanics to electrics/electronics. Whether e-mobility or hydrogen propulsion, the laser and photonics industry has seized the opportunity to change manufacturing processes and convince decision-makers of the undisputed benefits of photonic tools in the relevant production chains. And since most applications, e.g., in battery manufacturing and their use for emobility, started from scratch, the most profitable manufacturing tools could and can be used directly. It turns out that it makes sense not to transform an existing process from the "pre-laser age" into the modern age. The laser has undoubted advantages over other tools in these production chains. When you talk about processing speed, low energy input, automation, which is very easy to implement with lasers, energy efficiency and freedom from contact, then there is no getting around the laser as a tool. This paper gives an overview of some applications in battery production and e-mobility from the perspective of a supplier of sensors and processing tools. The focus is on laser welding, as process monitoring and control play an important role here and describes the intersection between industrial requirements and photonics when it comes to efficient production tools for tomorrow's mobility. It is about sensor technology, it is about beam shaping, it is about material processing, and it is about AI.

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Section: Photonics In the Field Of Battery-powered Vehiclesmentioning

confidence: 99%

Meeting the challenges in e-mobility with laser welding and sophisticated system technology

Kogel-Hollacher,

Reiser,

Nicolay

et al. 2024

Laser-Based Micro- And Nanoprocessing XVIII

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“…If the sample is within the measuring range of the measuring head, both surfaces of the sample vibrate synchronously, and the thickness measurement is not negatively affected. Interferometric sensors are also used for quality assurance and process control in industrial laser material processing [1], [2], [3], [4], [5], [6], [7]. The emissions from the interaction zone are not coherent with the light generated by the sensor, so there is no effect on the measurement.…”

Section: Sensor Technology 21 Spectral Interferometrymentioning

confidence: 99%

Interferometric surface inspection with movable measurement spot: high-speed OCT imaging for thickness and topography in industry

Kogel-Hollacher,

Nicolay,

Mieth

et al. 2023

Optical Technology and Measurement for Industrial Applications Conference

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The increasing demands in industry, for example for products in the consumer electronics sector or for assistance systems in cars, and the continuous development in semiconductor are leading to significant miniaturization in electronic components. These requirements are inevitably also transferred to ultra-precise manufacturing and thus ask for monitored production steps. In the context of Industry 4.0 and other developments in the context of modern production sensors to supervise production steps are crucial. An essential component here is non-destructive testing (NDT) and specifically optical metrology.Complete 3D measurement of objects using white light interference in mass production is time consuming and therefore not well-suited for use as a means of inline inspection. In addition, the long measurement cycles with complex sequences generate large amounts of data and the effort for processing the data must also be included in overall considerations. The Flying Spot Scanner (FSS) intelligently avoids these disadvantages and is therefore ideal for inline inspections.To meet the need of additional, even complex and time sensitive measurement tasks, Precitec Optronik has developed the Flying Spot Sensor. The active measuring head was specially developed for in-line use and ideally complements the spectral interferometric sensor to form a smart inspection system. The light from the sensor is coupled into the measuring head via a light guide and deflected by a mirror system, a so-called galvanometer scanner. Finally, the light passes through a telecentric lens, which serves as a focusing module on the outward path and as a measuring aperture for the reflected light. Due to the movable mirror system, the measuring light beam can be deflected at different angles and thus the measuring spot can be freely positioned within the field of view of the lens. Long paths of linear axes are replaced by short rotary movements, resulting in an extreme reduction of the measuring, or scanning time. By using specialize focusing modules, the Flying Spot Scanner can be adapted to different application scenarios. These optics are characterized by a low curvature of the focal plane, very small telecentric errors and a very large depth of field. The measurement system can also be used in two operating modes, a thickness mode, or a distance mode. The two operating modes can be selected at will via the digital interface, which means that the switching process can be easily integrated into an automatic measuring sequence.

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“…One potential inline monitoring technology that overcomes this limitation is optical coherence tomography (OCT). 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].…”

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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Low-coherence interferometry in laser processing: a new sensor approach heading for industrial applications

Cited by 8 publications

References 7 publications

Meeting the challenges in e-mobility with laser welding and sophisticated system technology

Meeting the challenges in e-mobility with laser welding and sophisticated system technology

Interferometric surface inspection with movable measurement spot: high-speed OCT imaging for thickness and topography in industry

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

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