Green Light for New 3D Procedure
Selective laser melting (SLM), also known as laser beam melting or laser-powder bed fusion (L-PBF), has already proven itself as an additive powder-based manufacturing process in various industries such as medical technology, turbomachinery manufacturing, aerospace and automobile manufacturing. This procedure is primarily used to process steels, titanium and aluminium alloys, as well as nickel and cobalt alloys. The Fraunhofer Institute for Laser Technology ILT in Aachen, Germany, is planning to further develop SLM within the framework of a research project in order to make it more suitable for the additive production of components made from pure copper and copper alloys.
Depending on the surface properties, pure copper reflects the greatest part of laser radiation generated in the typical wavelength range of approx. 1 µm. Therefore, only a very small part of the irradiated energy is coupled into the material and is then available for the melting process. The reflected laser radiation can damage the components of the system. In addition, the absorption rate of infrared light increases dramatically when the material passes from the solid to the liquid state, thus providing for an unstable and discontinuous remelting process. With green laser light and its wavelength of 515 nm, the absorption rate of copper is many times higher. In this case, a laser with a significantly lower output power would suffice. Moreover, the laser beam could be more narrowly bundled so that the new SLM procedure could be used to produce significantly more filigree components. Because there is no corresponding green beam source currently available on the market that satisfies the boundary conditions for the SLM procedure, the Fraunhofer ILT department is developing the laser themselves.
A laser is being planned for so-called single-mode operation that operates with a maximum power of 400 watts in continuous operation with a green wavelength (515 nm) of very good beam quality. By the end of 2017, a laboratory setup is to be built for the Aachen team to further develop these processes within the framework of the research project. Their goal is to create a stable process that industrial users can implement to create complex geometries with cavities and undercuts out of pure copper in a direct, additive manner. The procedure can be used for highly efficient heat exchangers and heat sinks or for the small series production of filigree and complex electrical components.