They Like It
Snap-locking sphere container inspired by Demi-sphere by wizard23 is licensed under the Attribution - Non-Commercial - Creative Commons license.
© 2010 by wizard23
Instructions
Because I'm on holydays and did not bring my RepRap with me I could not test the optimal angle for the best fit. So I prerendered some angles: 5, 7 and 10 degrees that I think would work well. Just make sure you print the two corresponding parts. metasphere_7degrees_larger_part.stl and metasphere_7degrees_smaller_part.stl for example.
FYI: for the illustrating screenshot I took an angle of 40 degrees to make the principle clear but I think it would have to bend way too much if you printed it like that so I prerendered only small angles that I think would work.
I'll be back home in a day and printing some of these will be one of the first things I'll do when I get back but I wanted to see if the thingiverse community is even faster with printing it :)
UPDATE: I printed the 7 degrees version. Results: The snapping is not snapping enough and the angles in which the two parts meet does not stabilize the parts so the sphere can be deformed too easily. I adapted the design by modifying the cones into straight cylinders deviating even more from the original shape but maintaining a flat base. I uploaded the new design and a stl files for a 15 degrees version that should snap nicely...I hope...well its only iteration 2 :)
UPDATE: these versions don't work too well...the second does not have a flat base...I followed another approach and came to a nice snapping ball: thingiverse.com/thing:3272
