Hola amigos, checking back in for the 3D printing assignment where we were tasked with printing an impossible object small enough to fit in a gumball capsule, using two different methodologies.

When deciding on impossible objects, I decided to choose an articulating animal. My first choice was a caterpillar, which I began printing on the Prusa fused deposition modeling printer. Since the bottom of the caterpillar was flat, I chose to print bottom to the plate without a raft.

My first try was much too small, so small that all the articulations broke as I tried to move them. The hinges needed to be made bigger to function properly, aka to articulate. I printed again, on a scale large enough to fit straight across flat in the housing, however the joints were still too thin and my caterpillar once again wouldn’t move :(. At this point, I decided to make the move to another articulating animal with stronger joints: the slug. I printed one at 50 mm in length before realizing that with the full articulation I could increase the length as it would bend within the housing. My final sized slug was 100 mm in length, printed on the Prusa FDM, which ended up fitting perfectly. After this, I printed three copies of the slug in one go-around. The first and second time I tried doing this the print got very messed up, with the nozzle getting clogged after the print wasn’t sticking (probably because I wasn’t using a raft). Third time was the charm, because the three prints finally turned out (with a raft this time)! Unfortunately, the spacing was a little weird and the printer was trying to print an extra raft in between the second and third slugs, which made a little material drag onto slug three. It isn’t perfect, but they are close enough to identical for this assignment!

Once I had gotten the sizing right on the Prusa using FDM, I began stereolithography printing in parallel to my remaining slugs. For this, I used the Formlabs printer. This one was a little trickier as it didn’t utilize 3DPrinterOS, but it was simple enough to redownload the file on that printer, scale, and get the settings right (raft and supports as suggested by the software). It was interesting to see the software automatically orient the slug at such a strong angle (45º?), which we had been told previously could help the print come out cleaner. The resin and tank already in the printer were a good fit for this print (Grey Resin V4), so I didn’t have to change those and was able to get the print started. The SLA slug took much longer than the FDM ones, but it turned out great. Very smooth in terms of layering (impossible to see the layers!) and the joint sizing worked out so that the slug was still able to articulate. I was very happy to see that the SLA printer hadn’t fused the model like I had been told to expect for articulating models.

In terms of post processing, for the SLA slug, I washed and cured it according to the guidelines for the specific resin, then was able to clip off the supports. For the FDM slugs, I really only had to remove them from the rafts and they were ready to go.

 

 

 

 

 

 

 

 

I’ve had a bit of experience with 3D printing, but had never messed around with factors like layer height and infill too much. My main struggle is getting the print to turn out right, as typically the chosen supports are not enough (glad to know there’s an option that does all orienting, supporting, rafting in one!). I like that this assignment taught me the technical names of the 3D printing techniques I have experience with. Typically I would just refer to my experience via printer name (MakerBot, Prusa, FormLabs (resin printer)), but was largely unaware of titles like FDM, which will definitely help going forward the next time I get asked for more details on my experience!

Cost: ~$10.66 per slug

Material: $0.10 (1x FDM) + $0.61 (6x FDM failed) + $0.61 (3x FDM) + ~$2 (1x SLA) = $3.32

Labor: $7.5/hr @ 3 hrs = $22.5

Overhead/equipment use: $5/hr @ 5.5 hrs = $27.5