A systematic comparison between green and infrared laser for laser powder bed fusion of pure copper through a benchmark artefact

Laser Powder Bed Fusion (L-PBF) is one of the well-established Metal Additive Manufacturing (MAM) technology that is highly applied in aerospace, medical and automotive industries due to its advantages such as high design freedom and low tooling cost. A new generation of heat exchangers and electrical coils with complex geometries can be imagined if pure copper parts can be effectively fabricated using L-PBF. However, producing pure copper parts with no defects by L-PBF is a challenge due to the low optical absorptivity of pure copper to infrared radiation and its high thermal conductivity. To produce dense copper parts the power of the infrared laser (available in most commercial L-PBF machines) must be increased above 400W which can strain the optics of the laser system. Using a green laser instead of an infrared laser is another solution as copper has a high optical absorptivity at this wavelength. In this work, a benchmark artefact with features relevant to thermal management and electromagnetic applications was printed with two state-of-the-art commercial L-PBF systems, each equipped with either an infrared or green wavelength laser. A thorough geometrical investigation was conducted on the benchmark artefacts, and it was concluded that the pure copper artefact manufactured by the green laser system had a higher geometrical accuracy and included minimal defects compared to the artefact produced by the infrared laser.