For this week’s project we’re 3D printing an impossible object. Once I saw the chains made by the previous students, my first instinct is to make a piece of jewelry that could be worn. Personally my favorite accessories are earrings, so I started out designing a long earring.
My first design. The ball inside two rhombuses is supposed to be trapped but spin around freely.
The first design printed out.
The first design looked okay but there were a series of issues. The main issue was that it didn’t fit in the capsule, but I didn’t want to shorten it because this length is based on the length of earrings. There were other issues such as the ball not spinning as smoothly as I wanted, but the main issue is the one that’s difficult to overcome.
My decision was to give up on the idea of making a pair of long earrings (since it’d be difficult to fit in the capsule), instead I’m making a pendant that I could end up putting at the end of an earring. I liked the idea of a sphere spinning in a cage, so I switched the design to the second design below.
The second design made in Fusion. The size is based on the biggest pendant I have.
I first printed using the Prusa printers with PLA. The first time I printed with diameter of 14mm, and the ball would fall out of the rhombuses too easily. The second print I printed with a diameter of 16mm and the ball was difficult to detach from the rhombuses. So in this final print, I used a diameter of 15.5mm, which I found was the optimal diameter in that the sphere would not fall out easily. However, later when I was trying to color it, I realized that the sphere could actually be snapped out with a bit of force. I was concerned that this would make the print no longer qualify as “impossible”, but the rhombuses still had interlocking designs so it was okay.
This also made it very convenient to color. I wanted the rhombuses and the sphere to be different colors. My first instinct was to tape the sphere and spray paint the whole thing, which would be a very tedious process. But now I can just snap the sphere out and color them separately.
Spray painting the rhombuses. I picked the metallic golden spray paint because of how it could cover up the texture of the print.
Before I spray painted the print, I sanded it with very low grain sandpaper just to sand off the bumps from the supports.
The supports removed from the print.
I was really satisfied with the gold/white color palette and felt like gold with any other color might be too much, so I decided to keep the sphere white.
The final project.
I then repeated the process 3 more times to create 4 identical PLA prints, and for the last one, I printed using the SLA printer instead.
First attempt on printing SLA.
I found it very difficult to print this design on the SLA printer since the parts would always fuse together. I tried several attempts. The first attempt seen above the whole top part (where the supports are) was fused together and it was very difficult to separate. My second attempt was to print the ball separately from the star, but because the start would fuse together and breaks when I try to separate them, it was impossible to put the ball in there. Then I tried printing it all together with a smaller ball, which is the final print seen below. This time I was able to separate the print from the supports, but this print also has a few flaws (it’s slightly broken and the ball is still fused to the sides so it wouldn’t move). However, this print is still the most resembling of my desired print. The biggest lesson learnt here is that SLA printers are not great with these intricate moving parts because of how easily the pieces fuse together.
The final SLA print along with all the other prints.
I attempted to use the Fuse1 printer, but we couldn’t find the build chamber and we couldn’t find a lab technician that really knew how to use the printer.
Trying to print on Fuse1
I wrote the paper slips by hand since there wasn’t an URL involved. I decided to name it “Moon in a star” at the end because of how the rhombuses look like a star most of the time.
Overall, I’m very satisfied with the FDM printed parts, but SLA might not be an optimal method for this print.
The final prints in their capsules.
Cost Estimation
4 FDM Printed Pieces: 4*$0.12 = $0.48 (based on the estimated cost on 3D PrinterOS)
1 SLA Printed Piece: 3.2mL of Resin * $200/Liter = $0.64 (based on Grey Pro Resin price on Formlabs)
Labor Cost: 3 hours * $7.25/hour = $21.75
