Development of SLM process using 200 W blue diode laser for pure copper additive manufacturing of high density structure

Near-infrared lasers, which are mainly used in the SLM (selective laser melting) method at present, have a low absorption rate for copper, making it difficult to fabricate a 3D structure of copper. To solve this problem, we have developed a new 200 W blue diode laser (wavelength: 450 nm), that has a high absorption rate for copper. The SLM system with the blue diode laser has been developed. In addition, the additive manufacturing of pure copper was performed under the control of parameters such as scanning speed and hatching distance. The purpose of this study is to fabricate a high density 3D structure of pure copper. The fabricated 5 × 5 × 5 mm3 size sample was cut perpendicular to the scan pattern, polished, and observed to measure the density of the cross section. In the beginning of the experiment, voids (porosities) appeared in the body of the copper 3D structure with the cross-sectional density of approximately 92%. Therefore, we changed the parameters to suppress the void formation in the process. Although we focused on the density of the structure for achieving the purpose, the density did not increase beyond 94%. Therefore, we changed the scan pattern of the laser irradiation. As a result of the optimization of the process parameters, especially by the effect of the optimization of the scan pattern, a high density structure of the density of approximately 99.1% was achieved.