Nanoparticle Bed Deposition by Slot Die Coating for Microscale Selective Laser Sintering Applications

The minimum feature size in most commercially available metal additive manufacturing (AM) processes is limited to ~100 microns which poses a fundamental challenge in fabricating complex 3D micro-components. The authors have developed a microscale selective laser sintering (µ-SLS) process with the goal of fabricating these microproducts with 1µm minimum feature size resolution. To achieve near-net shaped sintered features, the powder bed layer should not be more than one micron thick. This paper presents the development and testing of a powder bed deposition mechanism using a slot-die coater. Metallic nanoparticles uniformly dispersed in a solvent were used in this study. A viscocapillary coating model was used to predict the wet thickness of the powder bed based on the coating gap. Experimental results revealed that uniform sub-micron layer thicknesses were achieved by optimizing the process parameters such as flow rate, coating speed, coating gap, and die gap. The novel approach discussed in this paper enables the implementation of a robust coating mechanism for high throughput AM.