This was definitely a good experience getting more familiar with the 3D printer, its limitations, and its possibilities. I first experimented with a cute little owl pencil holder, which failed due to the small size required for this project’s objects. I settled on an “Impossible Ball in Cube” made by the user lucasdredge on Thingiverse (https://www.thingiverse.com/thing:265454) which consisted of a hollow cube that had a ball whose diameter was larger than its sides inside of it. I gained a better understanding of supports, infill density, layer height, and base supports (rafts, brims , and skirts) in this iterative process. It was also interesting learning how to use the resin printer (SLA printing) and learning its advantages and disadvantages over using FDM 3D printing. The greater detail on the resin printer ultimately swayed my partner and I to use it for our detailed chess piece on the final project, so this assignment was a good prelude to the final assignment.
I consulted the TAs and Lab Assistants about the feasibility of the Owl pencil holder in a scaled down fashion, and their advice was that it probably wouldn’t work, but that I should give it a try on the FDM printer and see what happened. I used a low layer height (0.15 mm) because of the detail on the piece, and sure enough, the scaled down owl was quickly destroyed once the intricate mesh of the middle of the owl body was being extruded.
After this, I looked for some impossible shapes that would be more easily scaled down into the required small shape to fit in the gumball capsule. I settled on the impossible cube because of its simple geometry, which made me think that it would print well in a smaller size:
I decided to first print the shape using the FDM printers. I shrank the dimensions to a 3 cm x 3 cm x 3 cm cube after measuring the gumball capsule size. I first tried to print the shape without supports, as they seemed extensive to be put in each face of the shape. When I did this, however, the shape ultimately failed at the top corners:
I first tried to fix this by decreasing the layer height to 0.15 mm, thinking this might be the issue (it was the default 0.2 mm before). Unfortunately, I got the same problem:
This second failure convinced me to begin printing the shape with supports, so that’s exactly what I did. This produced the full shape! Unfortunately, the supports were very well connected to the faces, so taking them off took a lot of effort:
After removing the supports, the resulting impossible cube fit well into the gumball capsule!
Because I oriented the ball at the bottom of the cube so it wouldn’t print “above the frame,” there was a weird imperfection on the bottom of each of the balls, but there wasn’t really a way around this while still keeping the structural integrity of the print (this was repeated with the SLA resin print):
I repeated the FDM print three more times, taking off the supports and raft each time (and printing in different colors!). I did my final print on the SLA print. This was my first time using the SLA printer, and Charlie as well as lab techs were very helpful in assisting me in the process! The supports were very different for the SLA shape (easier to take away), and the printing time was only about an hour.
My final five shapes turned out great and all fit well into the gumball capsules! This was a shorter time commitment than past projects, but still prepared me well for the final project despite not having much 3D printing experience coming in!
Cost Analysis
Each PLA print on the FDM printers cost only about 20 cents, so even including my messed up prints, the total was only $1.40. Resin costs a bit more ($1 per print) [1]. I spent about three hours on this project, so at $15 an hour, the labor cost was $45. This combined set therefore cost about $47.40.
The printers themselves are more expensive (FDM is about $2000, SLA is about $3500), but because these are not raw material costs, they have not been included in the product costs for these items [2].
References
- Arceo F. Resin vs filament cost in 3D printing! [Internet]. 3Dsolved.com. [cited 2022 Apr 16]. Available from: https://3dsolved.com/resin-vs-filament-cost-in-3d-printing/
- FDM vs. SLA: Compare filament and resin 3D printers [Internet]. Formlabs. [cited 2022 Apr 16]. Available from: https://formlabs.com/blog/fdm-vs-sla-compare-types-of-3d-printers/
