Update 2/9/2021 - I apparently made updates to this thing, which I never published. The updates are pretty significant, and the new version belongs on it's own Thingiverse page. As I'm somewhat lazy and lacking in free time, it may take a while to publish. That being said, you can access the Tinkercad files here: https://www.tinkercad.com/things/jFNy7TUHkie

This is a Raspberry Pi Cluster case, which I've dubbed "MultiPi" (Get it? Multiply? Hardee, har, har!)

1. Print the Upper and Lower, and put a RasPi in it!
2. Print the base for stability!
3. Print the Middle anytime you need to add another Pi!

This is still a thing in progress... Files may change!!

P.S. While you can technically stack 10, 20, or even 100 Raspberry Pi's using this case, it's not really recommended due to instability issues.
You've been warned!

EDIT (5/27): I've updated all .stl files. Here are the changes:

1. Flattened the top of the Upper and the bottom of the lower, mostly to make printing easier (reduced chances of warping).
2. Redesigned all three pieces with the objective of making the Middle a little easier to print.
3. Widened the case a bit, to allow more airflow, and to allow easier removal of a RPi.
4. Added a different middle piece, which has no holes for video/audio, since most clusters' slave nodes aren't used for such.
5. Adjusted the size of the power, HDMI, and audio holes.