Most metallic laser welding processes use a laser beam
incident perpendicular to the work surface, which
maximises power density and gives a symmetrical heat
profile. For absorptivity however, a perpendicular laser
beam is not the most energy efficient processing angle.
Absorption increases with incidence angle, from a
minimum at 0° up to a maximum at Brewster’s angle.
For a 1070 nm fibre laser welding 316L stainless steel,
this predicts an improvement from approximately 21%
to a potential maximum of 67%.
Potential benefits include reduced-power processing,
with smaller, cheaper lasers, with the attendant benefits
of reduced equipment costs, running costs, and reduced
cooling requirements (and hence reductions in running
and equipment costs).
Previous work on tilted laser welding has generally
involved simply altering the angle of the welding head
to create an off-axis beam. This method improves
absorptivity, but also alters the spot shape, distorts the
thermal profile, reduces power density, and alters the
velocity and cooling effects of the shield gas. The
effects on absorptivity alone were impossible to isolate,
and the energy improvements negligible.
In this investigation, a welding process was designed to
isolate and control the incidence angle absorptivity
effects, with all other variables, that were also altered in
previous work, left unchanged. Firstly, the reflectivity
principles underpinning the work are presented and
justified. Creation of the required laser beam shapes is
then evaluated via ray optics simulations. This is
concluded with the design and testing of a physical
optical array with beam test results presented.
History
School
Mechanical, Electrical and Manufacturing Engineering
Published in
2021 ICALEO conference proceedings
Source
40th International Congress on Applications of Lasers & Electro-Optics (ICALEO)