I have not actually printed this because I don't have a 3D printer yet!
I'm not sure why I made a mouse wheel... it just sounded fun. I'm pretty sure your mouse will eat it, so it's not very practical, but it was a fun project nonetheless. I am completely new to 3D modeling, so I apologize if it isn't perfect. I tried to break it up so that it wouldn't need much support structure, if any.

The last two files aren't needed. One is to demonstrate the final result, the other is a zip folder with all the parts!
I hope everything works. Let me know if I need to change anything. First combine the two Wheel pieces. There are rods on the big wheel piece that will hopefully fit into the holes on the flat wheel piece. Then slide the cylinder rods of the Base pieces through the middle circles on the Wheel and snap them together. Lastly, snap the two outer frame rods of the Base pieces together.