In the OEDK we have a small gumball machine that dispenses small containers with toys or knick knacks inside. Ours dispenses impossible objects. This homework was to 3D print such an “impossible object”, something that could not easily be manufactured by another means (too small, internal voids, etc). For my impossible object, I chose the mathematical Seifert surface, a ribbony structure that loops back on itself into one piece and whose edge represents a knot.
This is the Figure 8 Seifert surface I found on Thingiverse. I set it up on a Makergear and on the Objet to get two different prints. I’ve been wanting to try the Objet poly jet printer with its smooth results. I thought, why not make the Objet print in Tango black? Then I’ll have a flexible surface. Easy… is that all?
Mesh fills in the holes.
The Makergear chugged along and I set up another in pink, just in case it messed up something. Well, I reached the minimum feature size possible for the Makergear printer. In one area of the surface, the wall was so thin that the slicer didn’t add material there. Instead of solid wall, the print started to generate mesh to fill the gap. I printed the piece at a 38 mm maximum dimension to give some wiggle room, but I remeasured to use the entire space and printed again. At 45 mm maximum dimension the walls were just thick enough to print solidly.
As for the Objet print, the printer overheated because apparently the Objet needs a fan pointed at it while it runs. When I came back in the morning to clean the piece, I found it unfinished. I decided to learn to use the water jet on it anyway, and as I sprayed the flexible piece it just disintegrated. Next round, doing a rigid piece.
Sad remains of a failed print.
I reprinted the Objet print with the white rigid material and it worked great! This time it didn’t fall apart in the waterjet and turned out beautifully smooth. Now I have two Seifert surfaces for the gumball machine. The Objet print is much more uniform than the Makergear’s and shows very little visible layers. The Makergear print, in contrast, had suboptimal connection between the round rim and the flat layers because it somehow sliced them as separate components. Furthermore, the tear-away support left residue bits on the print that were difficult to remove. Overall though, I am satisfied with how these turned out.
Splendid surfaces!
Cost analysis: I spent 2 hours at $20/hour, so $40. The Makergear prints were very cheap, about 7 cents per print, so $0.21. The Objet prints were $14.70 and $17.51, much more expensive. In total, my pieces cost $72.42.
