3D printing
I attended Session 2 for the group activity, where people were excited to get hands-on with the 3D printer. However, due to our rush to start printing, we didn't correctly set the right filament type in both the printer and slicer, which resulted in a big spaghetti ball. This experience taught us that next time, we need to carefully read the manuals and understand the machine before using it.
Nozzle clogged due to wrong filament setting.
For my individual assignment, I used the Prusa MK4S for all of my printing. Being a beginner, I wanted to focus on the basics and leave the Formlabs printer for later exploration.
To satisfy the non-subtractive requirement, I started by designing a cage in Onshape. This gave me good practice with the circular pattern repeat feature and helped me get the hang of parametric design. I revolved the cross-section to form a single beam and then repeated the beam to form the cage. In retrospect, I should have extruded the cross-section to form a uniformly thick beam, which would allow the beams near the top area of the cage to have better strength. My current design has thinner beams near the top, which I had to compensate for by adding another disc at the top.
Notice how beams became thinner near the top.
Next, I wanted to print a feather inside the cage to add a poetic touch. I designed a feature using linear repeats and boolean interaction of a "leaf" shape. I directly printed the feature onto the cage, but it turned out too small.
Feature is barely visible
I enlarged the design and printed it separately. This time it worked perfectly. I have unforunately overwritten the CAD file with another design and could only recover an *.obj file. I should use the version history feature to backup more often in Onshape.
Separate the feature (model)
Combining the feather with the previous cage design created a mini sculpture.
A touch of poetry (model)
Next, I wanted to challenge myself by printing something more difficult. I designed a 4D cube, also known as a tesseract, and placed it in the same cage. The CAD work was much more difficult with this design. I had to use several boolean operations to get the cube inside the cube, and connecting their vertices required creating new planes that are not coplanar with any existing faces.
Cube inside cube inside cage (model)
Finally, I wanted to introduce a movable element, so I printed a ball inside a cube cage. The ball's diameter is the same as the cube's interior dimension so it won't fall out.
Ball inside cube (model)
Notice the support material inside the cube. I used the default snug fit support provided by PrusaSlicer, and it worked as expected: it was easy to remove and prevented any spaghetti from overhang issues.
3D scanning
I scanned a bionic mannequin in the lobby of the Media Lab using the Polycam photogrammetry app on my iPhone.
Here is the original object. Even for human eyes, it's hard to tell what the actual shape is without invoking my knowledge of human anatomy.
The mannequin in the Media Lab lobby.
The mirror surface confused the photogrammetry software and caused it to treat convexity as concavity.
Notice the concavity on the face and chest area.
I found the result aesthetically provocative, resembling a starving zombie. So I proceeded to tilt the figure backward and add an organic support to transform it into a horror sculpture.
In order to make the support structure part of the final print, I extensively customized the support structure to ensure:
- There was no vertical or horizontal gap to the model.
- Double-walled support (this seems to be the strongest option PrusaSlicer offers).
- Minimum spacing in support layers for additional strength.
Extensive customization (project)
I attempted a few different sizes and materials. The largest one printed with PETG turned out the best. The middle-sized print used the default organic support settings, which suffered "broken leg" failure, while the small version lost too much detail.
Zombies of different sizes and materials.
I really appreciated the feedback from our TA:
I find this disturbing.
-- Alan Han