Researchers have developed a hybrid process capable of faster speeds during laser welding, and higher deposition rates during metal 3D printing.
The new process combines laser beam welding with gas metal arc welding – a wire-based process – to deliver speed and cost-effectiveness similar to that of wire arc additive manufacturing (WAAM), and precision similar to that of wire laser material deposition (WLMD).
Arc-based processes are traditionally not as precise as laser-based processes, as the arc cannot be focussed to the same precision as the beam.
However, in the new process, the researchers enclose the arc using coaxially oriented annular laser radiation, in such a way that the arc cannot break out of this ‘collar’, forcibly guiding it and increasing its precision.
It is for this reason that the researchers, from Fraunhofer ILT, have named the new process ‘COLLAR Hybrid’, with COLLAR also being an acronym for the ‘coaxial laser arc’ used.
One process, two applications
The process has applications in both metal 3D printing and welding.
The Fraunhofer ILT researchers will be using it to further develop metallic 3D printing, while their colleagues over at the RWTH Aachen University Institute for Welding and Joining (ISF) will be using it to enhance welding.
‘COLLAR Hybrid can be used to develop direction-independent 3D printing applications for building both small and large components,’ explained Max Fabian Steiner, a research associate at Fraunhofer ILT. ‘In addition, due to the higher levels of precision enabled by the laser-guided arc, the amount of post-processing required for this process is significantly less than that of WAAM.’
In welding, the new process could be used to achieve speeds twice that of arc welding, according to initial tests. What’s more, arc welding equipment typically needs to be rotated when processing corners or curves, leading to more path programming effort. This is not the case for COLLAR Hybrid.
‘The optics of the new process enable welding in any direction,’ confirmed Steiner. ‘In addition, we expect that new, less complex preparations at the joining partners will be sufficient when welding thick sheets.’
Schematic setup of the COLLAR (coaxial laser arc) Hybrid processing head. (Image: Fraunhofer ILT)
The degree to which the laser and arc are each used in the new process can be varied flexibly.
For example, with a majority or purely laser process (switching the arc to low power or off completely), finer structures can be deposited. However, with a majority arc process, coarser structures such as wide ribs or large areas can be deposited significantly faster, more cost-effectively and with lower energy input.
The process could also lend itself to welding/building reflective materials such as aluminium or copper, for which more expensive beam sources producing blue or green laser light are continually being developed.
‘For example, I can use a majority arc process to break up the aluminium oxide layer, which has a melting temperature of 2,200°C, and then use a majority laser process to accurately process the aluminium layer underneath, which only has a melting temperature of 660°C,’ Steiner explained.
Interested? Learn more!
Those interested in the COLLAR Hybrid process can learn more at an upcoming specialist congress organised by the Germany Welding Society from September 19 to 21 in Koblenz.
The German Welding Society, primarily know as DVS ( Deutscher Verband für Schweißen und verwandte Verfahren e. V.), funded the ‘KoaxHybrid’ project in which the new process was developed.