New 3D Printing Process for Copper Materials
Researchers at the Fraunhofer Institute for Laser Technology ILT presented a procedure for the additive production of copper materials using Selective Laser Melting with green light. The process is intended to process highly conductive, pure copper, for example in the small series production of electrical components.
Selective Laser Melting (SLM), also known as Laser-Beam Melting or Laser-Powder Bed Fusion (L-PBF), is an additive powder-bed-based manufacturing process that has already proven itself in various industries, such as medical technology, turbomachinery, aerospace and automotive engineering. At present, this technology is primarily used to process steels, titanium and aluminium alloys as well as nickel and cobalt alloys.
Researchers at the Fraunhofer Institute for Laser Technology ILT in Aachen now want to further develop SLM as part of a research project to make it more suitable for the additive production of components made of pure copper and copper alloys. This project is supported by the AiF Arbeitsgemeinschaft industrieller Forschungsvereinigungen "Otto von Guericke" e. V.
Pure copper is interesting for end users because no copper alloy has a comparably high electrical and thermal conductivity. The Fraunhofer ILT is therefore developing a specially designed laser beam source by the end of 2017, which no longer uses infrared but green light.
At a usual wavelength of approx. 1 µm, pure copper reflects most of the laser radiation, depending on the surface properties," explains Daniel Heußen, a research associate at the Rapid Manufacturing Group. Therefore, only a very small portion of the radiated energy is coupled into the material, which is then available for the melting process. The reflected laser radiation can damage the components of the system. In addition, the absorption coefficient at the transition of the material from the solid to the liquid state increases rapidly in infrared light, thus creating an unstable and discontinuous remelting process.
Green laser light
Green laser light with a wavelength of 515 nm behaves differently, since the absorption coefficient of copper is many times higher. The fact that a laser with a significantly lower output power is sufficient to switch to green laser light speaks for itself. In addition, the laser beam can be sharply bundled, so that the new SLM process can be used to produce much more complex components.
Since there is no corresponding "green" beam source on the market that meets the boundary conditions for the SLM process, the department of beam source development at the Fraunhofer ILT built the laser for "SLM in green" themselves. A laser for so-called single-mode operation is in the planning stage. It is to operate with a maximum output of 400 watts in continuous operation (cw) with a green wavelength (515 nm) and a very good beam quality. By the end of 2017, a laboratory construction of a plant for "SLM in green" will be built, which the Aachen scientists will use to further develop the processes within the framework of the research project funded by AiF.
The aim is to create a stable process that allows industrial users to produce complex geometries with hollow structures and undercuts from pure copper by directly applying additive technology. This is of particular interest for the development of highly efficient heat exchangers and heat sinks or for the small series production of filigree, complex electrical components. "Inductors are particularly suitable for inductive heat treatment in industrial production. Because they are usually produced in small quantities with high complexity and many variants, they are perfect examples for additive production," Heußen adds.
“SLM in green" offers the possibility of producing complex structures in a much more efficient and reproducible way than conventional techniques currently used in the field of jewelry design. Compared to other additive processes such as electron beam melting (EBM), the scientists hope to achieve a much higher detail resolution and greater cost-effectiveness in production. The green laser is not only suitable for copper, but also for the processing of non-ferrous and precious metals in the jewelry industry. ”Until then, however, it will be necessary to overcome a number of hurdles in process and plant development and to develop a deeper understanding of the processes involved in using the new wavelength. This is the goal of the current publicly funded project, which runs until mid-2019," Heußen concludes.
This article was first published by Elektronik Praxis.
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