ANALYSIS: BEAM SHAPING
New refractive beam shaping methods for laser materials processing
Joerg Volpp and Adrien da Silva, at the Luleå University of Technology, investigate beam shaping possibilities for high-power processing
Co-authored by Alexander Laskin, from Adloptica
beam in one layer to create, for example, several laser spots, tophat profiles or donut profiles.
Beam shaping technologies open up new possibilities and processing options for controlling heat input during laser materials processing. For high-power applications, beam shaping is usually done through either beam oscillation or by manipulating the spatial intensity distribution of the
Refractive optics for high- power laser applications Refractive beam shaping, which uses either mirrors or lenses, enables nearly lossless laser energy transfer through refractive optics, with a high flexibility of energy distribution in one plane or along the beam axis, for example between single laser spots, which has been shown to improve process quality. Recently we’ve installed and
Figure 2: High-speed images (top) and vapour channel appearance (bottom) at different beam shapes produced with FoXXus with several beam waists along the optical axis: a) two distant beam waists, b) four beam waists and c) two close beam waists.
tested Adloptica’s QuattroXX and FoXXus refractive optics in the laser laboratory at Luleå University to explore the effects of beam shaping on laser material processing at high power. Both optics are capable of splitting a laser beam into up to four separate beams. The QuattroXX produces spots beside each other, while the FoXXus enables manipulation of the beam waist distribution along the beam axis (see figure 1). For both optics, the distance between the spots is defined by the optical setup, while the intensity in each spot can be manually changed by rotating the optical elements relative to each other.
Figure 1: Optics and beam measurements of up to four beams next to each other (top, QuattroXX) and along the beam axis (bottom, FoXXus)
22 LASER SYSTEMS EUROPE AUTUMN 2021
Bridging the gap A widely known challenge in laser welding is gap bridgeability. Due to its typically small dimensions, a high intensity laser beam can transmit through the gap
between the joining partners. This leads to a loss of energy and a reduced energy input for the welding process, which can be interrupted or lead to a reduced penetration depth, lack of fusion and thereby reduced mechanical properties. Using the beam shapes enabled by the QuattroXX, it was possible to increase the bridgeable gap width from 0.1 to > 0.4mm in the used setup. Two dual-phase steel sheets (DP800 and DP1000 at 1.1mm thickness) were joined in butt joint configuration at a laser power of 3kW (15kW IPG fibre laser) and a processing speed of 3m/min, welded in the focal position of the beam. As the energy input can be
shifted to the joining partners without gap transmission losses, the optic’s additional feature of varying energy densities between individual laser spots also opens up new possibilities in joining dissimilar
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