3D metal printing involves building a metallic object layer by layer through the deposition of molten metal. This technique is advantageous in that it results in limited material wastage. Moreover, metal 3D printing techniques have shown more benefits when it comes to the direct fabrication of complex 3D structures, particularly, the micro thin-walled systems which possess a relatively complex cavity. Specifically, droplet-based 3D printing- a novel direct-writing technique that has numerous applications, such as printing of flexible circuits, advanced electronic components and metal parts- has become the center of research owing to the fact that it does not require expensive equipment, has low energy consumption and is environmentally friendly. Nonetheless, the surface of the formed parts produced using this technique have a tendency to have scalloped shape of metal droplets, hence a challenge in printing parts with high-quality inner surfaces.
To this effect, researchers at Northwestern Polytechnical University led by Professor Lehua Qi in collaboration with Dr. Ni Li at California State University developed a novel hybrid manufacturing method to fabricate tubes with ultra-high inner surface quality. They achieved this by combining the merits of soluble cores and droplet-based 3D printing, based on inspiration from conventional casting processes. Their work is currently published in Journal of Materials Processing Tech.
In brief, the research method employed commenced with the development of an experimental system with a rotating and translating receiver stage, so as to satisfy the forming principle of uniform droplet rotation deposition manufacture. Next, the researchers advanced a selection strategy of rotating angles, followed by multiple deposition experiments purposed to assess the effects of two processing parameters on the quality of formed parts. After the processing parameters were well tuned, a hexagonal metal part was fabricated directly. Lastly, the quality of the fabricated parts was characterized by the standard Archimedes method, industrial CT, and laser scanning confocal microscope, respectively.
The standard Archimedes test showed that the density of the formed part was up to 98%. The industrial CT scanning results also proved a porosity-free inner structure. In addition, the inner surface roughness was measured to be ~Ra 4.38 μm by using a laser confocal microscope scanning, and the roughness was only ~0.37% of the droplet diameter. These measurement results indicate that the authors have achieved a new milestone in the development history of metal droplet printing.
In summary, Dr. Hao Yi and colleagues presented a new and novel technique for manufacturing metal tubes with high-quality inner surfaces via deposition of aluminum droplets over soluble cores. To achieve this, they developed an experimental system with a four-axis receiver stage for use in fabricating the metal tubes. Altogether, their work has presented a future potential method to directly fabricate complex metal tube structures with high inner surface quality.
Hao Yi, Lehua Qi, Jun Luo, Daicong Zhang, Ni Li. Direct fabrication of metal tubes with high-quality inner surfaces via droplet deposition over soluble cores. Journal of Materials Processing Tech, volume 264 (2019) page 145–154.Go To Journal of Materials Processing Tech