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Optical Methods for In-Process Monitoring of Laser Beam Welding
University West, Department of Engineering Science, Division of Electrical and Automation Engineering. (PTW)ORCID iD: 0000-0001-5734-294X
University West, Department of Engineering Science, Division of Automation Systems. (PTW)ORCID iD: 0000-0002-8771-7404
GKN Aerospace, Trollhättan, Sweden.
2014 (English)In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, 1-9 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper addresses the issue of evaluating and selecting optical sensors to be integrated with a 1μm laser beam welding system. The method used for this evaluation is mainly a survey of relevant research litterature. The result of this work is a matrix showing the different methods and distinct features related to relevant process conditions that can be estimated or detected with respective methods. This evaluation also includes considerations on the required sensor bandwidth in relation to inertia and time constants in the physical process.

Place, publisher, year, edition, pages
2014. 1-9 p.
Keyword [en]
Optical methods, process monitoring, laser beam welding
National Category
Engineering and Technology Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Mechatronics
Identifiers
URN: urn:nbn:se:hv:diva-6854ISBN: 978-91-980974-1-2 (print)OAI: oai:DiVA.org:hv-6854DiVA: diva2:755934
Conference
The 6th Swedish Production Symposium
Available from: 2014-10-15 Created: 2014-10-15 Last updated: 2017-02-09Bibliographically approved
In thesis
1. Optical detection of joint position in zero gap laser beam welding
Open this publication in new window or tab >>Optical detection of joint position in zero gap laser beam welding
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents an experimental study on how to track zero gaps between metal sheets to be joined by laser beam butt welding. Automated laser beam welding is gaining interest due to its ability to produce narrow and deep welds giving limited heat input and therefore less distortions compared to other processes, such as arc-welding. The automated laser beam welding process is however sensitive to how the high power laser is positioned with regards to the joint position. Deviations from the joint position may occur due to inaccuracies of the welding robot and fixturing, changes in joint geometry, process induced distortions, etc. Welding with an offset from the joint position can result inlack of sidewall fusion, a serious defect that is hard to detect. This work develops and evaluates three monitoring systems to be used during welding in order to be able to later control the laser beam spot position. (i) A monitoring systemis developed for three different photo diodes, one for the visual spectrum of the process emissions, one for the infrared spectrum, and one for the reflected highpower laser light. The correlation between the signals from the photodiodes and the welding position relative to the joint is analysed using a change detection algorithm. In this way an indication of a path deviation is given. (ii) A visual camera with matching illumination and optical filters is integrated into the laser beam welding tool in order to obtain images of the area in front of the melt pool. This gives a relatively clear view of the joint position even during intense spectral disturbances emitted from the process, and by applying animage processing algorithm and a model based filtering method the joint positionis estimated with an accuracy of 0.1 mm. (iii) By monitoring the spectral emissions from the laser induced plasma plume using a high speed and high resolution spectrometer, the plasma electron temperature can be estimated from the intensities of two selected spectral lines and this is correlated to the welding position and can be used for finding the joint position.

Place, publisher, year, edition, pages
Trollhättan: University West, 2017. 64 p.
Series
Licentiate Thesis: University West, 2017:15
Keyword
Laser beam welding, Optical sensors, Joint tracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10684 (URN)978-91-87531-50-7 (ISBN)978-91-87531-49-1 (ISBN)
Supervisors
Available from: 2017-02-10 Created: 2017-02-09 Last updated: 2017-02-10

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Sikström, FredrikNilsen, Morgan

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