These past two weeks, I was assigned to utilize the 3d printers available to print an impossible object. The impossible object would be something defined as having one of the following: hinges/interlocking features, moving parts, internal geometry, or very high complexity. For this assignment we were assigned to choose an existing object on Thingiverse that qualifies as an impossible object and print 5 pieces while utilizing at least 2 different 3D printing processes. The challenge was that I had to fit each print into its own gumball capsule. The object I chose to print was an articulated dragon.
https://www.thingiverse.com/thing:5775735
The first method that I decided to use was FDM printing utilizing the Bambu printer. Upon loading the dragon file into the Bambu slicer I noticed that the file was very large so I decided to scale the model down, however I did not know what scale size would maximize the space in the capsule. So to begin I printed out a 0.3 scale model of the dragon using white PLA. To make sure that the file would print correctly I turned on generating auto supports when slicing the model.
After the model finished printing I began to remove the supports off of the print. To remove the supports I used my fingers to pick at the supports in open areas and in tight nooks I used a dental scraper.
Me cleaning the supports off with a dental scraper.
Upon clearing off all the supports I noticed that the print was articulating more than I had initially anticipated and that the 0.3 scale print was not filling up enough space within the capsule, so I decided to increase the scale to 0.4 and reprint.
An image of all 3 scaled dragons that I printed from left to right (0.3, 0.4, 0.5, 0.6).
Upon removing the supports off of the 0.4 model and placing it in the capsule there seemed to be additional space within the capsule so I decided to print 2 more prints, one at 0.5 scale and another at 0.6 scale. After the prints were done and the supports were removed I attempted to place them into the capsule, the 0.5 scale model fit but the 0.6 scale model was a little too large to fit inside the capsule. After finalizing the scale to be at 0.5, I printed 3 additional 0.5 scale models using the bamboo printer.
The two images above are of the Bambu printer printing the other three 0.5 scale dragons.
An image of the 3 dragons before post processing.
The second method I chose was SLA printing and I utilized the resin printer from Form Labs. Prior to sending my print I had spoken to a few of my classmates and they said the SLA models they printed were far more rigid and would snap when pressure was applied. So for this print I chose to begin with a 0.4 scale model, as I was unsure if the articulating pieces of the model would work as intended, since all the models only fit into the capsule due to their flexible nature. Unfortunately, my fear came to be as the model was far too inflexible and it broke when I attempted to move the articulating pieces. The resin I used for the SLA printer was the tough 1500.
Image on the left is how the dragon came out of the SLA printer after being washed and the image on the right is of me clearing out the supports right before the print broke in half.
After the SLA model broke I spoke with Dr. Wettergreen on what to do next as the SLS printer was currently offline and inoperable and the assignment was to utilize 2 different 3d printing techniques. He said that instead of using the SLA printer I could utilize a different FDM printer, not the Bambu, and that would also satisfy the requirements for this assignment. So I chose to utilize the Prusa FDM printer to complete my last 0.5 scale model. For this print I chose to use clear PLA, with the same auto generated support settings. Cleaning of the supports for this model was not a pleasant experience, as the supports inside crevices were not easily identifiable and they seemed to be adhered more compared to the supports of the Bambu printer. I attribute this difference in support to the quality of the prints as the Bambu printer has a higher resolution compared to the Prusa printer.
The image on the left is of the clear PLA dragon and the image on the right is a white PLA dragon next to a clear PLA dragon.
Below is my cost model for this assignment with the total cost being $418.48 including all labor and materials.
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | White PLA roll | $19.99 | https://us.store.bambulab.com/ | 2 | $39.98 |
| Clear PLA roll | $28.00 | https://www.amazon.com/ | 1 | $28.00 | |
| Tough 1500 Resin | $149.00 | https://formlabs.com/ | 1 | $149.00 | |
| Dental Scraper | $5.58 | https://www.amazon.com/ | 1 | $5.58 | |
| Labor | Prototyping Engineer (You!) | $36.48/hr | https://www.ziprecruiter.com/ | 4/hr | $145.92 |
| Overhead | Facility Cost (Machine Time – 3d printer) | $50/month | https://apps.txrxlabs.org/join-us/ | 1 | $50.00 |
This cost model includes the material for my failed SLA print, which attributes to a significant portion of the cost. Additionally all the labor in this model is how long it took me to actually send the print off to the printers and the post processing time for all the models. Below is an image of my clean workspace and my final submission.
