Trumpf, headquartered in Ditzingen, Germany, reports that it plans to incorporate the new Extreme High-Speed Laser Deposition Welding (EHLA) method, developed by Fraunhofer Institute for Laser Technology (ILT), into a number of its Additive Manufacturing systems. According to the company, EHLA is significantly faster than conventional Laser Deposition Welding.
Depending on component size, Trumpf stated that it has various laser machines which are candidates for EHLA. The company’s TruLaser Cell 3000 is suitable for small and medium-sized components, while the machines in the TruLaser Cell 7000 Series are suitable for large ones. Apart from these turnkey systems, manufacturers can also integrate the EHLA method into their existing systems.
“For EHLA, we can draw on similar techniques to those we’ve been using for Laser Deposition Welding,” explained Antonio Candel-Ruiz, an expert in laser surface methods at Trumpf in Ditzingen. “The Fraunhofer Institute for Laser Technology developed and patented EHLA with the primary aim of executing coating processes very quickly with low layer thicknesses for rotationally symmetric components.”
“For large-area coating tasks, lasers have until now lacked the necessary speed,” stated Candel-Ruiz. In addition, the minimum layer thickness achievable using conventional Laser Deposition Welding is around 500 micrometers.
In conventional laser deposition, the laser generates a weld pool on the surface of a component and fuses the metal powder, coaxially added simultaneously, to create the required shape. The powder then fuses with the surface, gradually forming a protective coating.
By contrast, in the EHLA method, the laser strikes the powdery filler material above the weld pool, heating the material nearly to its melting point while it is still on its way to the component. Consequently, the particles melt faster in the weld pool. This makes it possible to use energy much more efficiently.
Whereas normal laser deposition welding can coat only 10- 40cm2 per minute, the EHLA method achieves rates of over 250cm2 per minute. In addition, much thinner coatings with layer thicknesses of 10- 300 micrometers are now possible. What’s more, EHLA permits a much finer laser focus, rendering the process considerably more energy-efficient.
“Our diode lasers and our disk lasers are suitable for EHLA, depending on the laser focus required,” added Candel-Ruiz. With diode lasers, a focus of around 1mm is possible; with disk lasers, a focus as small as about 0.2mm. In addition to the laser beam source, another decisive factor is that the machine has a rotational axis which permits high speeds.