The use of a ns-pulsed, high repetition rate green laser for SLM of 99.9% pure Cu

The most common laser type used in selective laser melting (SLM) machines is continuous fiber laser emitting at 1 m. The low optical absorptivity of Cu to ~1 m wavelength renders pure Cu a highly demanding material for SLM . The low optical absorptivity along with high thermal conductivity causes unstable processing conditions when standard SLM machine are used with pure Cu. Conversely, Cu has a much higher optical absorptivity at the green wavelength. Until recently, high power green lasers have not been available for material processing. This work investigates the use of a novel ns-pulsed fiber laser operating at the second harmonic (532 nm) for SLM of 99.9% pure Cu powder. In particular, the laser source operates at 30 MHz repetition rate providing ns regime and up to 110 W average power. The green laser is implemented to a bespoke open SLM platform. Results show that cubic specimens with densities >99.5% could be achieved.