Tomer Gluck of FennecLabs recently posted a tutorial on 3D printing transparent objects such as lenses on desktop FDM 3D printers. While there are many transparent filaments available for FDM (fused deposition modeling) 3D printers, there are few transparent 3D prints that come out of the popular desktop machines. This is because FDM printers don’t create 100% solid parts, partly for material usage reasons and partly for technical limitations. The material-saving infill patterns of 3D printed parts create uneven light diffusion, which is why they can’t be transparent. Even when setting the infill to 100%, there will usually be slight voids and gaps between the lines of plastic extrusion that inhibit the passage of light.
Gluck overcame those hurdles by adjusting the slice parameters of Cura to over-extrude just enough material to fill those voids. He set a very thin layer height of 0.05mm (50 microns) and a slow print speed of 24mm/s in order to create consistent layers, which were further squished together by a manual Z-height adjustment on the 3D printer after the first layer that removed any air gap between the extrusion nozzle and the part. The temperature was set to 255°C, the maximum limit of the Prusa ABS used in the tests, to encourage each layer to fully bond to the previous layer; thermoplastics can completely integrate when in their liquid form, so two layers that are fully bonded according to the technical definition are not two separate layers but one solid object.
This is evidenced by the rather clear objects revealed after a bit monotonous sanding and polishing with finer and finer grit sandpaper. The outside of each print was marred by the over-extrusion, but the settings clearly worked on the inside where it matters. He even printed a cavity mold of Mario in an effort to imitate a laser-etched glass block. Gluck’s 3D printed lenses won’t be finding their way into any NASA telescopes, but they’re good enough to focus parallel lasers, so their use in DIY projects could be extensive. This is actually quite a breakthrough because it confirms the technical feasibility of something that even most pro users thought was impossible. It’s likely that these 3D prints are also stronger due to their homogeneous molecular structures, which is its own totally separate benefit to printing 100% solid parts.
Discoveries that come from tweaking software settings are incredibly productive because they’re the easiest to disseminate to makers and researchers. Companies that write slicing software could incorporate these settings into an upcoming patch that includes 3D printing profiles optimized for transparency. This should also serve as a lesson to makers out there to really dive into the nitty-gritty of their slicing programs to learn how each parameter interacts with their 3D printer hardware and how it affects the look and mechanical properties of 3D prints. Ambitious makers don’t have to wait for print profiles as they can create their own. They can make their own mistakes and their own discoveries.