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Proceedings Paper

Online process monitoring at quasi-simultaneous laser transmission welding using a 3D-scanner with integrated pyrometer
Author(s): A. Schmailzl; S. Steger; M. Dostalek; S. Hierl
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Paper Abstract

Quasi-simultaneous laser transmission welding is a well-known joining technique for thermoplastics and mainly used in the automotive as well as in the medical industry. For process control usually the so called set-path monitoring is used, where the weld is specified as "good" if the irradiation time is inside a defined confidence interval. However, the detection of small-sized gaps or thermal damaged zones is not possible with this technique. The analyzation of the weld seam temperature during welding offers the possibility to overcome this problem. In this approach a 3D-scanner is used instead of a scanner with flat-field optic. By using a pyrometer in combination with a 3D-scanner no color-corrected optic is needed in order to provide that laser- and detection-spot are concentric. Experimental studies on polyethylene T-joints have shown that the quality of the signal is adequate, despite the use of an optical setup with a long working distance and a small optical aperture. The effects on temperature are studied for defects like a gap in the joining zone. Therefore a notch was milled into the absorbent polymer. In case of producing housings for electronic parts the effect of an electrical wire between the joining partners is also investigated. Both defects can be identified by a local temperature deviation even at a feed rate of four meters per second. Furthermore a strategy for signal-processing is demonstrated. By this, remaining defects can be identified. Consequently an online detection of local defects is possible, which makes a dynamic process control feasible.

Paper Details

Date Published: 4 March 2016
PDF: 7 pages
Proc. SPIE 9736, Laser-based Micro- and Nanoprocessing X, 97361J (4 March 2016); doi: 10.1117/12.2211705
Show Author Affiliations
A. Schmailzl, Ostbayerische Technische Hochschule Regensburg (Germany)
S. Steger, Ostbayerische Technische Hochschule Regensburg (Germany)
M. Dostalek, Ostbayerische Technische Hochschule Regensburg (Germany)
S. Hierl, Ostbayerische Technische Hochschule Regensburg (Germany)

Published in SPIE Proceedings Vol. 9736:
Laser-based Micro- and Nanoprocessing X
Udo Klotzbach; Kunihiko Washio; Craig B. Arnold, Editor(s)

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