Borromean Keyring

Made by auy

A cool mathematical object to hold my keys

Created: February 13th, 2018



The goal of my project was to combine my love of mathematics and my need to hold my keys. I also wanted to 3D print something that would not be possible to create through "normal" methods, and Borromean rings are such an object.


Research + Context

Nearly everyone has keys to carry around, but a single key is quite small, and many keys look very similar. A keyring should solve both of these problems: both identifying your keys, and providing a convenient way to hold them. Previously, I have had my keys on a lanyard, but it was a bit large, and many others have the same lanyard. So, I decided to make my own keyring. 


Aesthetic + Inspiration

My design is inspired by Borromean rings, which are generally shown as three circles linked in an interesting way. No two of the circles are interlocked, but all three together are linked. Borromean rings have been used in a number of designs throughout history, in addition to being an example in mathematical knot theory.


Process + Procedure

I already had an approximate design for my project, so when creating the CAD file I mostly had to consider the dimensions and shapes of the 3 rings. I sketched out my design, deciding it would be pretty small, around 2 inches. This choice was because the project is for a keyring, which needs to fit in my pocket. One challenge I faced was that I initially drew the rings as toruses in Fusion360, before realizing that Borromean rings cannot be created out of perfect circles. I then had to figure out how to make oval rings, which I did by drawing an ellipse and using the pipe tool. After making the model in Fusion360, I saved the file as an STL and sliced it with the Zortrax slicer. I printed it on the Zortrax printer, and it took about 3.5 hours. Finally, I removed the raft and supports using pliers and scissors. 



I learned that design is a challenging process, and that multiple revisions may need to happen before the final product. This project also helped me to be comfortable with both the NVBots and Zortrax printers. If I did this again, I would adjust the shapes of the 3 rings to be more symmetric. I'm also considering painting the rings to have a more colorful final product.





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99-359 Inventor and 3D Printing

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This workshop is a hands-on introduction to the expansive world of 3D printing. 3D printing is a popular and versatile technology for quickly prototyping ideas. Students learn prototyping basics an...more


A cool mathematical object to hold my keys