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OCT inspection to enhance automotive welding

The potential benefits of using optical coherence tomography (OCT) in remote laser welding for automotive construction are being investigated by a consortium of academic and industrial entities in a research project exploring alternative bonding technologies for raw body manufacturing.

The project utilises a Blackbird Robotersysteme scan solution consisting of an intelliWELD PR scan head from Scanlab, a ScanControlUnit and an OCT scanner. (Image: Blackbird Robotersysteme)

The RoKtoLas (Robot-Supported, Scanner-Based Optical Coherence Tomography in Remote Laser Welding for Process Chain Flexibility in Body Construction) project aims to investigate how OCT technology could provide more flexibility in automotive body construction, particularly in electro mobility, where current inflexible production structures are hindering the cost-efficient manufacturing of smaller volumes – an issue that has led to disappointing electric vehicle sales to date. 

Project partners Blackbird Robotersysteme, the Technical University of Munich's Institute for Machine Tools and Industrial Management, BMW, Emil Bucher, Applicationtechnology and OCT sensor maker Precitec, are therefore combining contactless OCT technology with additional photonic sensors to inspect welding processes, assess their results, and share/document this information within the manufacturing process.

‘Future-proof production systems and bonding techniques need to work flexibly, adaptively and with connectivity,’ stated Blackbird and affiliated company Scanlab in a press release. ‘To maximise efficiency and autonomy, machines will require much more information about their surroundings and the objects to be processed.’

The project uses a Blackbird Robotersysteme scan solution consisting of an IntelliWeld PR scan head from Scanlab, a ScanControlUnit and an OCT scanner, which employs single-point high-speed distance measurement based on interferometry. The OCT scanner is coaxially coupled in the weld scanner to employ ultra-fast workpiece scanning, allowing it to provide integrated edge tracking and seam topology measurement.

An OCT scanner can make a distance measurement ahead of, within and past the actual laser process zone. This includes, for example, individual analysis of the components yet to be welded and seam tracking of fillet welds, as well as exact detection and parameterisation of potential weld defects or imprecision during the weld process.

Such data means seam quality can be assessed and defects recorded, for example inadequate width, penetration, open pores and faulty positioning. This data can be used in a clock-period-neutral manner for quality assurance procedures that eliminate the need for downstream quality assurance steps.

‘It's conceivable the future will offer numerous additional application possibilities – even reaching beyond the auto industry,’ explained Dr Ulrich Munzert, CTO at Blackbird Robotersysteme. ‘In light of the automotive sector's demanding requirements, this research project now allows us to accumulate practical experience on simplifying manufacturing approaches and processes while weighing them against alternatives.’

The RoKtoLas project is sponsored by Germany's Federal Ministry of Education and Research under the ‘Photonics Research Germany’ research incentive programme and supported by The Association of German Engineers (VDI).

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