title: Closed-loop power and focus control of laser welding for full-penetration monitoring.
abstract: We describe a closed-loop control system ensuring full penetration in welding by controlling the focus position and power of a 4-kW Nd:YAG laser. A focus position monitoring system was developed based on the chromatic aberration of the focusing optics. With the laser power control system we can determine the degree of penetration by analyzing the keyhole image intensity profile. We demonstrate performance in bead-on-plate welding of Inconel 718 and titanium. The focus control system maintained a focal position on tilted and nonflat workpieces, and the penetration monitoring technique successfully controlled the laser power to maintain the full-penetration regime in the presence of linear and step changes of thickness. Finally we discuss the performances and the limits of the systems when applied to a realistic complex aerospace component.
authors.affiliation: School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom. f.bardin@hw.ac.uk
authors.forename: Fabrice
authors.initials: F
authors.lastname: Bardin
authors.forename: Adolfo
authors.initials: A
authors.lastname: Cobo
authors.forename: Jose M
authors.initials: JM
authors.lastname: Lopez-Higuera
authors.forename: Olivier
authors.initials: O
authors.lastname: Collin
authors.forename: Pascal
authors.initials: P
authors.lastname: Aubry
authors.forename: Thierry
authors.initials: T
authors.lastname: Dubois
authors.forename: Mats
authors.initials: M
authors.lastname: Högström
authors.forename: Per
authors.initials: P
authors.lastname: Nylen
authors.forename: Peter
authors.initials: P
authors.lastname: Jonsson
authors.forename: Julian D C
authors.initials: JD
authors.lastname: Jones
authors.forename: Duncan P
authors.initials: DP
authors.lastname: Hand