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Proceedings Paper

Compact multisensor laser scanning head for processing and monitoring microspot welding
Author(s): Moustapha Hafez; Karin Julliard; Sylvain Grossmann; Lino Olivetta; Thomas C. Sidler; Rene-Paul Salathe; Hans-Peter Schwob; Toon Blom; Willem Hoving
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Paper Abstract

In order to improve the reliability of micro-spot welding of metal parts in production such as e.g. in electron guns for TV picture tubes, real-time information about the evolution of the welding process should be available to allow on-line modification of the laser parameters. Such information can be derived from a set of sensors that are mounted on a laser-scanning head. Different sensors are used to monitor the optical fiber output power to determine the evolution of temperature during the spot welding process, to measure plasma emission and back-reflected laser light. A vision channel and a CCD camera are used to control the position of the laser spot on the parts to be processed. The compact scanning head is composed of a tip/tilt laser scanner, a collimating lens and a focusing lens. The scanner is fast steering, with a bandwidth of 700Hz, and can tilt by +/- 3.5 degree(s) with a repeatability better than 50(mu) rad. The settling time for maximum deflection is less that 10ms. The scanning lens is a newly developed focusing lens designed to replace commercial cumbersome scanning lenses such as F-(theta) lenses, which have large volume, weight and price. This lens is based on the well-known Cooke triplet design and guarantees a constant shape of the spot all over the scan surface and is specially well suited for high power beam delivery. The scan field achieved by the system is limited to 25mm x 25mm. The laser used for this application is a pulsed Nd:YAG laser delivered by an optical fiber to the optical head. However, the system can be adapted to different types of lasers. Laser micro-spot welding on copper substrate has been performed in the frame of the Brite-Euram project MAIL. Smaller tolerances (a factor of 2 less) on the spot diameters were obtained in the case of a sensor controlled operation compared to the case where sensor control is not used.

Paper Details

Date Published: 6 November 2000
PDF: 4 pages
Proc. SPIE 4088, First International Symposium on Laser Precision Microfabrication, (6 November 2000); doi: 10.1117/12.405717
Show Author Affiliations
Moustapha Hafez, Swiss Federal Institute of Technology/Lausanne (United States)
Karin Julliard, Swiss Federal Institute of Technology/Lausanne (United States)
Sylvain Grossmann, Swiss Federal Institute of Technology/Lausanne (Switzerland)
Lino Olivetta, Swiss Federal Institute of Technology/Lausanne (Switzerland)
Thomas C. Sidler, Swiss Federal Institute of Technology/Lausanne (Switzerland)
Rene-Paul Salathe, Swiss Federal Institute of Technology/Lausanne (Switzerland)
Hans-Peter Schwob, Lasag Industrial Lasers (Switzerland)
Toon Blom, Philips Ctr. for Manufacturing Technology (Netherlands)
Willem Hoving, Philips Ctr. for Manufacturing Technology (Netherlands)

Published in SPIE Proceedings Vol. 4088:
First International Symposium on Laser Precision Microfabrication
Isamu Miyamoto; Koji Sugioka; Thomas W. Sigmon, Editor(s)

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