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Joint tracking in zero gap laser beam welding using a vision sensor
University West, Department of Engineering Science, Division of Production System. (PTW)ORCID iD: 0000-0002-8771-7404
University West, Department of Engineering Science, Division of Production System. (PTW)ORCID iD: 0000-0001-5734-294X
University West, Department of Engineering Science, Division of Production System. (PTW)ORCID iD: 0000-0001-5608-8636
2016 (English)In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, 1-7 p.Conference paper, Published paper (Refereed)
Abstract [en]

The paper describes a robust vision sensor system that can find very narrow gaps between metal sheets to be butt welded together. The use of automated laser beam welding is seen as a key enabler for efficient manufacturing by enabling narrow and deep welds with a limited heat affected zone and low thermal distortion of the welded components. It is sensitive to positioning the laser beam with respect to the joint position. Even a small off-set from the actual joint could result in detrimental lack of fusion. The system comprises a CMOS camera with optic filters integrated in the welding optics and appropriate LED illumination of the work piece. By analysing the spectral emissions during welding, illumination and matching optic filters have been chosen in a spectral range where the process disturbances are relatively low. In this way it has been shown possible to detect the joint position even during harsh welding conditions. Preliminary results from the first experiments show promising results, however more tests will be performed using different weld geometries etc. to verify the robustness of the algorithm.

Place, publisher, year, edition, pages
Lund: Swedish Production Academy , 2016. 1-7 p.
Keyword [en]
Laser beam welding, joint tracing, narrow gap, butt weld
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-10162OAI: oai:DiVA.org:hv-10162DiVA: diva2:1052787
Conference
7th Swedish Production Symposium (SPS), Lund, Sweden, October 25-27, 2016
Available from: 2016-12-07 Created: 2016-11-23 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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Nilsen, MorganSikström, FredrikChristiansson, Anna Karin
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