3D Printed Fidget Toy

My friend in 3rd grade had this fidget toy that was made up of 12 cubes, all connected by a stretchy string. The toy could be pulled apart a small bit, then it would snap back together with the faces touching. I thought this was cool and wanted to see if I could 3D print something similar.

You will need:

• A 3D printer
• Filament (any color)
• Elastic Paracord (I bought mine at Amazon)

Skip this step if you want, I'm just explaining how I got the proportions for each cube on the toy.

In the reference image, each cube has a slit cut into the faces, each going about halfway through. I assume it goes slightly more than halfway, however, so that the cord has a hole to go through. The cord that I have has a thickness of 1mm, so I want to make the center hole about 2mm. Now, I just have to decide the remaining proportions. The Amazon page for the one I am basing this off has a review containing a picture of somebody holding one. Google says the average palm size is 3in, and about 4 cubes take up the length of the palm. 3in divided by 4 cubes is .75in per cube. .75in is about 2cm, so I'll just go with that. To make the hole in the center 2mm, I need the slits in the cube to be 1mm over halfway, so that combined, would form a hole of 2mm cubed. The stretchy paracord will then go through all the cubes, then tied with a knot at the ends. After starting printing, I found that the cubes were about 1.5 times the size I wanted, so the revised size is a 15mm cube. Even this seemed a tad bit large, so I shaved 2mm off all sides, leaving a 13mm cube. After I printed these, I needed to tie the rope multiple times to prevent from slipping through, so I narrowed the slits down from 2mm to 1mm wide.

I designed the cubes using Tinkercad, which is pretty easy to use and has a nice UI. The first thing you need to do is make the main shape of the module. I want the cube to be 13mm on each side, so I drag out the box and scale it down to a 13mm cube. I cut a 2mm slit that goes in 1mm past halfway, so it needs to be scaled to 2x13x7.5mm (13÷2=6.5, so 7.5mm). For the module that will hold the ropes, I copied the main module and scaled the slits down to 1mm in width. I also added a 3x3x7.5 mm box that basically sat on top of the bottom slit. This was so that the knot could easily slip in, but not slip through the cube. This will all depend on the width of the rope you bought. Ideally, you want the main slits to be 1mm larger than the width of your rope, and the knot cube would be the same width.

To 3D print, first you need to slice the model, or turn it into G-code that the printer can read. For this, I use Cura. I add both the models. I need 12, so I add 1 knot cube and 9 standard cubes. I then tweak the settings to help printing (15% infill, .1mm layer height). I also rotated so that one of the slits was facing directly down. This was so that I needed no supports (the top will bridge the gap). Off to the printer!

The first thing was to gather all the materials needed. I ended up printing 10 cubes with 2mm slits so that it was easier to push the rope through the hole, as well as 2 1mm slits so that the rope with a knot could not slip through. I started by pushing the string through the first 1mm cube. This was actually really difficult so I was glad I only had to do it twice. I then put the 10 2mm cubes on, which was not difficult. I capped it all off with the second 1mm cube. After I had all the modules on the string, I tied a simple knot on the free end of the string, then testing by tugging on both the string and the cube. I then cut the string, leaving a decent amount so that I could easily tie the knot. I also recommend looking up a stopper knot to tie. As you can see in the video, I fiddled with this knot for a while, trying to get the knot as close to the cube as possible. I eventually got it pretty close, leaving little slack so that the toy kept its shape relatively well.

If you wanted, you could sand and paint this, but honestly, I'm too lazy to do that right now. I may gift this to my 6 yo niece, and if I do I will update this with pictures of the sanded version. If you do sand, I recommend doing it BEFORE assembly. Then, after you sand and paint and do all that jazz, you can put it together. Again, if you do sand, then start at about 80 grit, then work your way up to wet sanding with 220+.

Anyway, that's it! I'm really happy with how this turned out, and I've found that this really helps me concentrate in class. Now, instead of clicking pens and making my classmates annoyed at me, I can play with this and concentrate on what the teacher is saying. I hope that this helps you, and if you have any tips or need help, you can leave a comment and I'll do my best to help. If you enjoyed it, please vote for me in the contest, I would really appreciate it. Thank you for reading!