For the 3D printing assignment, I 3D printed five wireframe pentakis dodecahedra to fit inside gumball capsules. This model was created by mathgrrl on Thingiverse.com. I used two different additive manufacturing methods, namely fused deposition modeling (FDM) and stereolithography (STL/SLA). I started by reviewing all of the resources the OEDK has on 3D printing and learning as much as I can about the process. Although not entirely necessary for this project since instructions are given, I wanted to get the most out of the 3D printing module. I had also never 3D printed with SLA before, and there was a lot of theory to learn regarding this manufacturing process. After lots of learning, I started the assignment.
The first thing I did was find a model on Thingiverse. I wanted to take advantage of additive manufacturing as a method to make abstract mathematical shapes come to life, so I ended up creating a catalan solid, which are a group of polyhedra dualing the Archimedean solids.
Wireframe pentakis dodecahedron on Thingiverse.com
I then measured the size of the gumball capsule using calipers. My measured dimensions are as follows:
Diameter: 1.821 in = 46.2534 mm
Height: 1.47 in
Height of cap: 0.678 in
Total height: 54.5592 mm
I modeled the capsule as a cylinder with a diameter equal to the diameter of the circular cross-section on which the cap sits.
The next step was to scale the model to the appropriate size. I did a uniform scale on both Bambu Studio and PreForm and played around with the dimensions. The constraint I put on my dimensions was that no dimension (x, y, z) could be larger than any of the two measured dimensions: the diameter (46 mm) or the length (54 mm). This somewhat rigorous analysis would ensure that the piece would maximize the space inside the capsule.
I scaled the model on Bambu Studio to the following dimensions:
43.2 mm x 41.6 mm x 41.1 mm
I scaled the model on PreForm to the following dimensions without supports using a 0.650 scale factor:
42.61 mm (x) x 43.1 mm (y) x 42.1 mm (z)
As can be seen, largest dimension of each model is smaller than the smallest measured dimension.
I then decided to print out the credits for the model. I used the text from a text file that came with the download and I copied and pasted this five times on a document with 12 pt font. I cut them out using the paper cutter in the laser cutter room, and then I folded the slips so that they would fit inside the capsules.
It was time to start 3D printing. As you probably realized by now, using supports would likely be a problem for these prints since they would be difficult to take out. For the FDM prints, I did a test without supports. Luckily it came out completely fine, so I printed three more copies. I made most of my pieces using FDM because it was much easier than the SLA. For the SLA, I debated whether to use supports or not. I got warnings on PreForm that the model was unsupported, so I added some and printed like that. I also printed one without supports to see how it would go.
FDM pentakis dodecahedron
Fits inside the capsule perfectly. I would say it definitely optimized the space inside.
The SLA print was the more challenging of the two. Firstly, it takes double the time with 0.1 mm layer heights, the largest layer height available. Second, washing and curing is required, which takes up some extra time and availability. Third, supports are much more vital in SLA than in FDM. My first SLA print finished; however conditions for it werent ideal since I was not available for a while after I started printing, so it had been left sitting out wet. The resin cures slowly when exposed to the light, which is why this was not ideal. This was the print with supports. I washed it and cured it once according to the instructions online by FormLabs. It was tacky once it came out of the UV chamber. This is probably due to premature curing, insufficient wash cycles, and insufficient curing cycles.
This print had internal supports, so I was worried about how I was going to take them out. At first I used flush cutters as recommended, which worked to remove the base. However, the internal supports remained. Conveniently, there were some tools that looked perfect for this job. I used this very thin allen key to pry the internal supports out through one of the holes in the wireframe. This worked surprisingly well, and I was able to take all of them out. I decided to cure and wash it for another 15 minutes. As a contingency, I printed another model without internal supports to see if the warnings on the slicer were false positives.
This tool was perfect for the internal supports
Unfortunately the first SLA print remained tacky after another round of washing and curing. This is most likely due to the resin curing while it was left out for hours. I noticed it had a less clear tint than the second print.
First SLA print. This one had internal supports that I successfully removed.
The second SLA print was done without internal supports, but the base remained. The lack of internal supports seemed to have a very minimal effect on the quality of the linkages at the top, where the slicer flagged as unsupported the most. Fortunately I was there to ensure the part was quickly put into the washer and dried for 10 minutes afterward. It was still tacky after washing and curing, so I cured it for another 15 minutes. This definitely worked as it was significantly less tacky afterwards. I sanded it to get rid of the residue from the supports using wet sanding.
Final SLA pentakis dodecahedron
Here is a photo of my clean workspace
Cost Analysis:
Since 3D printing is now being practiced at home, I want to do a cost analysis keeping this in mind in addition to the regular one in which access to a makerspace is assumed.
Raw Materials:
Clear Resin V4.1 (Form 3) 1 L: $159
PLA Basic: $19.99
Total: $179
Labor: 4 hours, $15 per hour: $60
Machine Time:
Bambu Lab X1C 3D Printer: $1119
FormLabs Form 3 3D Printer: $1999
Form Wash: $699
Form Cure: $999
Total: $4816
Alternatively:
Maker space monthly membership: $50
Grand total: $5055 (including machine costs) or $289
The bulk of the price for 3D printing is taken up by SLA printing, which is notoriously expensive.
