LIA NEWS
2kW single-mode wobble welding allows independent control of penetration and bead width. The high intensity of the single-mode beam results in efficient coupling and low spatter, even into highly reflective copper
Traditional mechanical fastenings with nuts and bolts add weight and cost – laser welding provides the answer going forwards. Initial installations focused on high energy
multi-kW multi-moded laser sources with limited success. Te requirements of this application require lap welds which are ideally suited to laser welding. However, the resulting welds oſten suffered from high heat input, poor overall control of heat input, inconsistency in weld profile and penetration and, worst of all, high levels of spatter. Improved solutions have been developed based on the specific challenges of individual manufacturers’ designs. In
instances where material thicknesses are low and the need for control of heat input is high, SPI’s nanosecond welding process offers an ideal solution (previous page, right). Using only 100W lasers, excellent welds can be made in 300µm copper tabs. Tis technique enables multiple spots to be made to give appropriate bonding to the focus area, using a spiralled spot. Control of heat input and penetration is extremely high, but welding time can be quite slow given the low average power when compared to multi-kW CW. For applications that require high productivity
Hairpin ablation of dielectric coating prior to welding using nanosecond pulsed fibre lasers offers a cleaner, faster and more repeatable result that wire brush mechanical removal
and the ability to weld through thick metal, the recent introduction of high-power single mode CW fibre lasers has enabled these welds to be done using an oscillation or wobble welding technique. Tis uses a very small focused spot that is rapidly oscillated to enlarge the weld area. Tis enables the width of the weld to be controlled independently of the spot size, allowing the weld to be tailored to the application. Te rapidly oscillating spot also has the effect of controlling the heat input and the stability of the key hole/melt pool. Te resulting weld tends to have greater consistency in weld profile, top bead appearance and lower spatter (above leſt and right respectively). A 2kW single mode fibre laser can now create welds that are up to 2mm in penetration, with exceptional quality, both in copper or aluminium.
Welding of two rectangular tips of hairpins can be achieved using 2kW single-mode wobble welding. The high-peak intensity enables high coupling with minimal spatter, and the beam wobbling mitigates fit up gaps
30 LASER SYSTEMS EUROPE ISSUE 42 • SPRING 2019
Hairpin ablation and welding for electric motors Another significant opportunity for lasers is in the manufacture of electric motors, particularly in the welding of the copper hairpins on the stator. Tese pins are typically coated with an insulating material that needs to be removed prior to welding. Conventionally, this has been done using mechanical means, such as through
wire brushes, but this is difficult to control and prone to maintenance. Tese coatings can be ablated effectively by nanosecond pulsed fibre lasers (below leſt), leaving no residual material while simultaneously getting the parts selectively down to bare metal, ready for the subsequent welding step. Tese pins come in various shapes and sizes
but are oſten in a rectangular form, with the long sides up to 6mm in length. Welding with high-power CW multimoded laser sources in the 4-6kW range are currently being adopted, but this proves to be a challenging application for several reasons, including fit up, the need for minimal spatter and the need for low heat input, so as not to burn the insulating material only a few millimetres from the welding zone. Again, the use of a 2kW single mode fibre laser using the beam oscillation technique offers an alternative that provides good control of heat input and limits spatter (bottom leſt). Tese examples are not exhaustive but reflect
the level of dependency and reliance that the e-mobility industry is placing on laser materials processing. Te success of the e-mobility sector, and inevitable need for increased manufacturing capacity, will result in significant demand for industrial lasers in the coming decades.l
Jack Gabzdyl is vice president of marketing and business development for SPI Lasers. He is a Fellow of the LIA and has been innovating and publishing industrial laser applications for over 25 years.
Ken Dzurko is general manager of SPI Lasers and is responsible for SPI’s business in North and South America. He is a former board director of the LIA.
@lasersystemsmag |
www.lasersystemseurope.com
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