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Fraunhofer scientists develop SLM for copper alloys

Research scientists at Fraunhofer Institute for Laser Technology ILT (Aachen, Germany) have solved the technical difficulties which were preventing the use of selective laser melting techniques on alloys of copper, opening up new possibilities in rapid manufacturing. A 1,000W laser was used in place of the conventional 200W lasers used in SLM in order to compensate for the heat dissipation of copper.

SLM is a rapid manufacturing technique particularly well suited to producing metal components of complex shape, some of which cannot be manufactured using conventional technology or can only be produced at very high cost. In the InnoSurface project, which is funded by the German Federal Ministry of Economics and Technology (BMWi), a research team at the ILT have succeeded in modifying the SLM process to make it suitable for copper materials.

In the conventional SLM process, metal powder is deposited in layers on a computer-controlled platform before being melted at the required points by a laser beam, bonding with the existing part of the component as it melts and re-solidifies. Although copper has a lower melting point than steel, it's lower laser light absorption and higher heat dissipation make conventional SLM impractical, as tiny balls of molten metal form during the process, creating cavities in the final component.

The ILT team compensated for this high heat dissipation and low absorption by using 1,000W in the place of the 200W lasers commonly used in SLM. The entire installation was also modified in order to prevent the high energy input from causing disruptions. The ILT team states that its next goal is to adapt the process for use on pure copper, which has a thermal conductivity almost twice as high as that of the Hovadur K220 alloy demonstrated.

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