Development of the selective laser melting process for pure copper with a green laser

Selective Laser Melting is an innovative AM process which capable of producing near net shape complex components and has been in the center of attraction for industries. The combination of design and manufacturing flexibilities associated with SLM and extra-ordinary thermal properties of pure copper has attracted industries associated with heat transfer applications. However, processing copper is still in developing stage and yet to be adopted by the industries. This is because of Copper’s elevated conductivity and its poor absorption for IR laser which are commonly integrated with industrial SLM Systems. Therefore, fabricating pure copper components using SLM is yet to be adopted by the industries. This thesis work was intended to encounter the low absorptivity of copper by employing a nanosecond pulsed green laser of wavelength 532 nm as an energy source in the SLM system. The present work also studies the effect process parameters namely laser power, scan seed, spot size, hatch distance and layer thickness on the SLM of pure copper. In order to do that an exhaustive experimental campaign was designed and specimens of 5mm X 5mm X5mm were built on a Prototype of SLM system equipped with a nanosecond pulsed green laser at 162 different combinations of parameters with two replicates. An optical model was also developed and validated experimentally that allowed to manipulate the laser beam diameter thus enabling to study its effect on the process. The integrity of the specimens was analyzed by measuring the relative density of the specimens. The effects of process parameters on the surface roughness were studied as well. The highest relative density achieved was >98% at a laser power of 100W, scan speed of 300 mm/s, spot size of 100 μm, layer thickness of 50 μm and at hatch distance of 40 μm. The results obtained on the prototype system were then used to set up a newly developed Print Green 150 SLM system manufactured by 3D-New Technologies, Italy. Preliminary experiments were also carried on the industrial machine and categorical analysis was made on the specimens.

Selective Laser Melting (SLM) is an innovative additive manufacturing (AM) process capable of producing near net shape complex components and has been in the center of attraction for industries. The combination of design and manufacturing flexibilities associated with SLM and extra-ordinary thermal properties of pure copper has attracted industries associated with heat transfer applications. However, processing copper is still in developing stage and yet to be adopted by the industries. This is because of copper’s elevated conductivity and its poor absorption for infra-red (IR) laser which are commonly integrated within industrial SLM Systems. Therefore, fabricating pure copper components using SLM is yet to be adopted by the industries. This thesis work was intended to encounter the low absorptivity of copper by employing a nanosecond pulsed green laser of wavelength 532 nm as an energy source in the SLM system. The present work also studies the effect process parameters namely laser power, scan seed, spot size, hatch distance and layer thickness on the SLM of pure copper. In order to do that an exhaustive experimental campaign was designed, and specimens of pure copper were built on an open prototype SLM system. The results obtained from these experiments were then used to set up a newly developed Print Green 150 SLM system manufactured by 3D-New Technologies. Preliminary experiments were also carried on the industrial machine and categorical analysis was made on the specimens.