Hello all and welcome back to my blog. This week we worked with 3D printing, but specifically 3D printing an impossible object. You might be wondering: how can you make an impossible object if its impossible? The trick here is that these objects are very possible to make… but only with a 3D printer. Impossible objects are ones that cannot be fabricated in one piece any other way.

For my impossible object, I wanted to do something a little more creative than just printing a known impossible object. An impossible object can also be one that has moving parts without having to put pieces together. I found a series of car models with rolling wheels built in on Thingiverse. I was excited to find that there was a model of my car, so I decided to print that one. I measured the gumball capsule to scale my object. Then, I did some math and edited the file to ensure that the smallest feature would not be less than 2mm, since the wheels were quite small. Then, I printed one object at that scale. Sadly, it did not work. The wheels just broke off and didn’t spin.

Image 1: Small Car Failure

Also, the object was too big. I tried printing a bigger version and it did in fact work, so the issue must have been how small I tried to print it. Since it didn’t work at such a small scale and I needed to make it even smaller, I moved on to something that was more sure to work at a small scale.

I had spent a decent amount of time trying to figure out how to make the car work, so I decided that I would just use an existing impossible object. I liked the ones that had an object inside of another object. I have always thought it would be cool to print a closed box with a ball inside of it, but I think for the purpose of this project it is more effective to print an open box where you can see the ball stuck inside.

I found a design on Thingiverse, edited the size to make sure it would work, and printed it on the FDM printers using Bambu PLA filament. This part, though very simple, was frustrating because all the printers were either taken or had some issues. I had to change out filament on a printer and it still didn’t work after that, and multiple printers had issues like updates needed which I am not particularly trained to know how to deal with.

Image 2: Preparation for Resin Print

Eventually, my scale sample print worked and fit pretty well in the capsule, so I didn’t have to do a second scaling print. I printed three more parts with the FDM printers. I also sent one to the queue on the resin printers, which was super long since everyone was using them and there are only two. This assignment was a bit hard to complete during this step since there aren’t a lot of printers in the OEDK right now, and a lot of people were using them for the first time while other design teams were using them as well. Additionally, there are only two resin printers and one SLS printer that requires a lab tech to use.

After a long wait, I still hadn’t been able to even start printing my resin print, so instead I printed one object with TPU. I have used TPU before and it is quite a squishy material, so I was wondering how it would work for my project. This print didn’t take long and was much easier to post process than the resin as well.

Image 3: Final FDM Prints and Capsules

Cost Analysis:

PLA Filament – $0.85 (from BambuStudio Slicing)

TPU – $1 (estimate)

Labor – 2 hours, $14.50 (by minimum wage)

Machine Time – 1h18m for Bambu Lab printer, 1h 38m for Formlabs printer

Total cost: $16.35

Total machine time cost: 2h 56m