Introduction
For this assignment, we were asked to choose an “impossible object,” or a 3D printed design that could only be achieved through additive manufacturing. For this task, I chose a double gyroid sphere on Thingiverse from the user DaveMakesStuff. This part is made from two separate pieces that are interlocked to form a sphere, and I saw it as an interesting challenge to print.
Initial Printing
I started this project with a preliminary print at 1/3 the size to understand how the supports would be generated below and inside the part. After printing, I noticed that it would be very difficult to remove the internal supports at such a small size, but I saw great promise in future prints, so I scaled it up to the initial size of 30mm in diameter and started the full-size prints.
The view of a Prusa starting my first 3D print of the semester!
FDM Printing – Prusa i3 mk3
Soon, I started my first full-size 3D print on the Prusa I3 MK3. My first print was a great start. My largest priority was learning if it would be possible to remove the supports from inside the print to make it feel like two separate pieces. Because of the size and the strength of the supports inside, I was unable to remove these, but I was able to “break free” the inner piece to allow some rotation within the outer piece. Additionally, I found that some of the supports were not fully effective at supporting the overhangs of the inner piece, so the inner piece was particularly low-quality in some areas. I knew that these were problems I might be able to overcome by adjusting the supports or by using other 3D printing techniques.
Three double gyroid prints using the FDM process.
Although I hoped to adjust some of the support properties to prevent similar troubles with my other FDM prints, I struggled to understand what I would need to accomplish. I figured that other prints may produce higher quality parts, so I continued to print with the Prusas despite not being able to significantly modify the support structures. For the FDM prints, I left some good room for improvement and iteration, especially once I become more familiar with slicing software.
Prusa I3 Mk3 Estimated Cost:
Single Part:
Filament: 10.42 g of filament $0.21
Lab Assistants: 20 min at $11/hr $3.67
Machine Time: 1:59:40 at $1.00/hr $2.00
Total: $5.88
Overall FDM Cost (3 Parts):
$17.64
SLA Printing – Form 3d Printers
Following my FDM prints, I chose to use an SLA printer (the Form printers in the OEDK Wet Lab) for my final two prints. These printers used very different supports than the FDM printers, which gave me great hope that they would better allow me to remove the internal connections and separate the two pieces. Once they came out of the 3D printer, I was extremely excited, because I could already tell that the SLA printer better suited the goal of my part. I printed two of the spheres using the SLA process, and after removing supports carefully on the exterior and interior of the shape, they both met my goals for the prints. The overall quality was much better, and the parts were easily separable with a small tool. I was very happy to be able to use another process after struggling with the FDM printers, and I learned how a different process can help engineers to achieve different design goals.
SLA prints with supports still attached. These supports are much smaller than their FDM counterparts.
SLA prints after the supports have been removed.
Form SLA Printer Estimated Cost:
Single Part:
SLA Resin: ~10 g $2.00
Lab Assistants: 30 min at $11.00/hr $5.50
Machine Time: ~3:00:00 at $2.00/hr $6.00
Total: $13.50
Overall SLA Cost (2 Parts):
$27.00
-Kenton Roberts
