RAIL: A 3D printed wrist-mounted cell phone case


DSC00978 DSC00979 DSC00977

Skills used:

Autodesk Inventor, spatial reasoning


This is a rather simple idea that I cannot seem to find anywhere, so I had to 3D print it.

I have a Samsung Galaxy SII cell phone, and I wanted an engineer-style case that pushed the limits of conventionality. Because I watch way too many movies about the future, I kept getting the image of some spy or astronaut with a wrist-mounted videophone. While almost all cell phones today have Skype, I surprisingly could not find a case that made this wrist-mounting thing happen. Using my android skills to expertly go to the app store and download a free app that rotates the screen 90 degrees, and a background that displays phone information (CPU usage, battery level, compass, etc.) in a fashion that fit the style, I began working on the case on Autodesk Inventor.

In the end, it turned out surprisingly well. After getting the print back, my excessive number of caliper measurements paid off, and the phone slid in without a hitch. I did, however, place the top groove too high, and cut the camera’s vision in half, as well as making the hole for the charging cable too small. I will eventually hit these with a Dremel, and that problem will fix itself.

For my first field test, I wore it, as well as my 3D printed glasses, light up duct tape tie, and laser-cut business cards to the rededication ceremony of the Frith first-year engineering design lab. While there, I met a number of my old professors, as well as the dean’s advisory board and corporate sponsors, who were attending to see how funding the Frith lab would be a good investment, and what freshman engineers could do. Everything was a huge success. One person even asked for me to email the IPT file for the 3D printed glasses to her, and another said that she was “surprised that I didn’t get a job offer on the spot.”

On my way back from this event, I walked by one of the upperclassmen living in my dorm. When I showed the wristwatch to him, he was rather stunned. After I said, “This makes me feel significantly more awesome,” he replied, “No, this makes you significantly more awesome.”

(The IPT and STL files for this have been made available here.)


    • My phone is now attached to my wrist, which makes it much harder to lose.
    • I generally wear an Apple iPod Nano attached to a watch case and use that as a watch and music player, and if I can switch over to a phone, it can take over this purpose and do more.
    • Just the idea of it feels so futuristic, and since Virginia Tech has WiFi all over the campus, I can use it as a mobile computer, as well as a video phone.
    • It looks absolutely amazing. The shape is sleek, and even when it is off, just having the screen attached to my arm looks quite awesome. It is one of those things you look and go “I know an engineer made this,” which was my whole idea from the start.


    • I did not do the best job attaching the straps, and they are rather loose in some places and tight in others.
    • Having two straps feels surprisingly uncomfortable, but I will get used to it.
    • The 3D printer material is extremely brittle, and taking this out means risking total failure.
    • I really wish I had measured the top better, because now I will have to Dremel it and ruin some of the sleek shape.

Opportunities for improvement:

Well for starters I need to attach clips and tightening tabs to the straps to make it more user friendly. After that, I have to get something better than a SII, and remake it with CORRECT measurements, a better latching system, and a side-mounted battery pack that can recharge the phone.


I really like it. I’m not sure quite why, but I like it. It has a number of flaws, and some wasted material, and I would love to redo this (possibly with a newer, better phone). However, I am really proud wearing it around campus; call it an “artist’s unconditional love.”

One thought on “RAIL: A 3D printed wrist-mounted cell phone case”

Leave a Reply