The “impossible” object I chose to 3D print is “Fish Fossilz,” published by muzz64 on Thingiverse. This object is essentially a set of jointed fish bones, which I believe would be impossible to manufacture as a single piece through any other one-step process.
Figure 1: Fish Fossilz examples from Thingiverse
Figure 2: Fish Fossilz immobilized by raft
The first time I printed this object, I mistakenly included the raft, which is useful for creating a good seal between the object and the platform, as well as an ensuring that the printer nozzle is extruding properly. However, for this particular print including a raft doesn’t work because it creates a rigid connection between all the individual fish bones and therefore immobilizes the joints.
Figure 3: Example of fused joint
The second time I printed this piece was mostly successful. Without any post-processing, some of the joints between fish bones were obstructed by excess filament, making them difficult or impossible to move. I wiggled these joints side-to-side to loosen them up some, then tried to rotate them about the joint’s axis. This eventually worked to break any filament holding neighboring bones together and get movement out of each joint that was stuck.
Figure 4: Top layer under-extrusion
Other imperfections from the print included excess filament around the edges of the fish and a thin in-fill on the top layers of the fish. The extra filament on the edges was easily removed by picking or filing it off gently. The problem with in-fill is only evident on the top of the fish, where you can see crisscrossing lines of filament from the printing process. It seems that the top layer didn’t create a seal for some reason. It’s possible that the nozzle started under-extruding on the top layers and failed to print entirely. Upon closer inspection, it looks like the detail in the fish tail is missing entirely, leading me to believe that the top layers failed to print, probably due to under-extrusion. It’s possible that the settings could have been optimized to make this surface more smooth or that it was just a random failure, but I felt that it was unnecessary to print again since the part is functional with approximately correct aesthetics.
This was a pretty cool assignment. I do some 3D-printing in my lab, which uses stereolithography techniques to polymerize a biocompatible solution into hydrogels housing living cells. I’ve also used fused-deposition-modeling (FDM) printers in lab for various other uses but have never had the chance to print a piece for fun. This homework was a chance to test the possibilities of FDM-based printing by making a more complex object made of interlocking parts. Exploring the inventive creations people posted to Thingiverse also opened my eyes to the power of 3D-printing.
