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Monitoring of Varying Joint Gap Width During Laser Beam Welding by a Dual Vision and Spectroscopic Sensing System
University West, Department of Engineering Science, Division of Production Systems. (PTW)ORCID iD: 0000-0002-8771-7404
University West, Department of Engineering Science, Division of Production Systems. (PTW)ORCID iD: 0000-0001-5734-294X
University West, Department of Engineering Science, Division of Production Systems. (PTW)ORCID iD: 0000-0001-5608-8636
University West, Department of Engineering Science, Division of Production Systems. IFN-CNR Institute for Photonics and Nanotechnologies, Physics Department, via Amendola 173, 70126 BARI, Italy. (PTW)ORCID iD: 0000-0002-6247-5429
2017 (English)In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 89, p. 100-107Article in journal (Refereed) Published
Abstract [en]

A vision and spectroscopic system for estimation of the joint gap width in autogenous laser beam butt welding is presented. Variations in joint gap width can introduce imperfections in the butt joint seam, which in turn influence fatigue life and structural integrity. The aim of the monitoring approach explored here is to acquire sufficiently robust process data to be used to guide post inspection activities and/or to enable feedback control for a decreased process variability. The dual-sensing approach includes a calibrated CMOS camera and a miniature spectrometer integrated with a laser beam tool. The camera system includes LED illumination and matching optical filters and captures images of the area in front of the melt pool in order to estimate the joint gap width from the information in the image. The intensity of different spectral lines acquired by the spectrometer has been investigated and the correlation between the intensity of representative lines and the joint gap width has been studied. Welding experiments have been conducted using a 6 kW fiber laser. Results from both systems are promising, the camera system is able to give good estimations of the joint gap width, and good correlations between the signal from the spectrometer and the joint gap width have been found. However, developments of the camera setup and vision algorithm can further improve the joint gap estimations and more experimental work is needed in order to evaluate the robustness of the systems.

Place, publisher, year, edition, pages
2017. Vol. 89, p. 100-107
Keywords [en]
Laser beam welding; Butt joints; Varying gap width; Vision sensor; Spectroscopic sensor
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-11898DOI: 10.1016/j.phpro.2017.08.014Scopus ID: 2-s2.0-85037711817OAI: oai:DiVA.org:hv-11898DiVA, id: diva2:1164274
Conference
16th Nordic Laser Materials Processing Conference, NOLAMP16
Funder
Vinnova, 2016-03291
Note

Funders: People programme (Marie Curie Actions) of the European Union's 29 seventh framework progamme (FP7/2007-2013), no 608473

Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2019-05-21Bibliographically approved
In thesis
1. Monitoring and control of laser beam butt joint welding
Open this publication in new window or tab >>Monitoring and control of laser beam butt joint welding
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser beam welding is one important technology in automated production. It has several advantages, such as the ability to produce deep and narrow welds giving limited heat induced deformations. The laser beam welding process is however sensitive to how the high power laser is positioned with regards to the joint position. Therefore, to achieve a seam without defects, the joint position needs to be measured and controlled. The laser beam welding process is also sensitive to variations in joint gap width. Costly joint preparations are required to achieve the tight fit up tolerances needed to produce high quality welds. However, the demand on joint preparation can be somewhat relaxed by allowing the joint gap width to vary and controlling the process. One way of doing this is to control the filler wire feed rate based on joint gap width measurements.This thesis presents experimental studies on how to track closed-square-butt joints and also how to handle varying square-butt joints in laser beam welding.

Different optical sensor systems are evaluated for their performance to estimate the joint position and the joint gap width. The possibility of detecting beam offsets is studied by using sensors systems based on a photo diode and on a spectrometer. Estimations of the joint position, to be used for closed loop position control, is studied by using a camera and external LED illumination. Variations in joint gap width is evaluated using a spectrometer, a camera and a laser profile sensor. Experimental results show that both the photodiode system and the spectometer system is able to detect beam offsets and that the beam position can be estimated with sufficient accuracy when welding closed-square-butt joints. It is also shown that the joint gap width can be estimated by the selected sensor systems and that the estimates can be used for controlling the wire feed rate in order to obtain a constant weld geometry and avoid defects related to the gap width.

Place, publisher, year, edition, pages
Trollhättan: University West, 2019. p. 84
Series
PhD Thesis: University West ; 27
Keywords
Laser beam welding, Optical sensors, Joint tracking, Varying gap
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-13650 (URN)978-91-88847-23-2 (ISBN)978-91-88847-22-5 (ISBN)
Public defence
2019-02-05, F104, Albertsalen, Trollhättan, 10:15 (English)
Opponent
Supervisors
Available from: 2019-03-15 Created: 2019-02-28

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Nilsen, MorganSikström, FredrikChristiansson, Anna-KarinAncona, Antonio

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