3D printed minimalist USB keyring
January 2014
About
I like the idea of carrying some useful data around with me wherever I go, and with USB keys getting smaller and smaller it's quite possible to get ones that will fit on your keychain.
With this in mind, I bought a SanDisk Cruzer Force with a metal casing in late 2013. Sadly, in early January the actual USB PCB came loose in my pocket and came away from the casing — it still worked but without the case it needed to be supported to read in a PC.
So I decided to 3D print a new case!
Process
Using Google Sketchup, I designed a small USB 'shim' to precisely fit the USB PCB, replacing the old, slightly bulky casing.
My design needed to be:
- Functional: fit into a USB socket and provide physical connection to the contacts
- Rugged: going to live in my pocket with my keys (metal)
- As small as possible: I don't like having a bulky keyring
Having recently discovered that Shapeways had begun printing in metal, I took the opportunity to give the process a go.
Revision 1
The first design was functional, just. It fit the USB PCB after a small amount of filing, and when plugged in it would register as a flash drive. Unfortunately, the metal 'lip' at the front would momentarily short out the 5V and GND pins on insertion. Some PCs handle this gracefully; others immediately power off. Upside-down insertion was also possible, which would short the USB device more permanently.
Revision 2
Revision 2 addressed these issues:
- Indentations pushed through to holes — allows USB PCB removal if it goes faulty
- Small 'horns' added to the front — prevents reverse insertion
- Front lip lowered — avoids instantaneous short circuits on insertion
- Tray width expanded slightly — USB chip fits without filing