Effect of input energy on densification for pure copper fabricated by SLM with blue diode laser

Abstract

Selective laser melting (SLM), a recently developed additive manufacturing method, is capable of directly fabricating three dimensional models from a CAD data, which a laser beam is irradiated on the powder to melt and solidify on a powder bed. In SLM, although a fiber laser with the wavelength of near infrared ray (IR) is employed, it is difficult for pure copper to fabricate a complex shape because of its low light absorption rate to copper. Therefore, we have developed an SLM system using a blue diode laser with absorption rate about 6 times that of IR laser and demonstrated for it possible to fabricate pure copper. In this study, we fabricated pure copper by using the developed blue semiconductor laser of 450 nm wavelength and near infrared semiconductor laser of 915 nm wavelength, respectively, and the effect of laser wavelength in SLM was clarified. Furthermore, in order to optimize the densification of the pure copper material of the sample fabricated by the SLM system, the input energy such as the laser scanning speed and the hatching distance were varied. As a result, the correlation between the energy density of the laser and the relative density of the prepared sample was clarified.