Development of a novel powder sheets printing process towards the next generation of additive manufacturing: the role of laser defocusing

To address safety and labour-intensive challenges in laser powder bed fusion, a novel Metal Additive Manufacturing using Powder Sheets (MAPS) method is employed. By examining the formation mechanism of the melt pool, we discovered that MAPS printing utilising a negative defocus strategy achieves a favourable conduction mode. This approach results in the fabrication of crack-free SS304 samples with over 99.65% relative density and elongated grains. These phenomena are caused by diverged laser power density distribution and decreased entrainment of byproducts such as vapour into the melt pool, as observed by the laser-powder sheet in-situ interaction. Furthermore, the productivity of MAPS increases when printing using the negative defocus setting compared to the scenario without defocus and productivity also increases with the decrease in scanning speed, attributed to a larger amount of metal particles entrained into the melt pool. This study provides insights into the novel MAPS manufacturing for functional metal components.