This is a smaller, 4-leaf redesign of emmett's totally amazing Preassembled Iris Box (http://www.thingiverse.com/thing:1811143). After studying emmett's design carefully and with some advice from emmett himself, I managed to design a 60mm diameter version that prints faster. I also increased the internal clearances somewhat to make it less challenging to print. Like emmett's, it prints pre-assembled and without supports. Thanks, emmett!
Update: I added and STL file for just the leaf in response to someone wanting to replace a broken one. I'm not sure how easy it'll be to get it assembled into place, though.
Update: In my original version, the outer sphere was a little wobbly when closed and could cause jams. I've updated it to help prevent this problem. I've also included the Solidworks (2011) model for anyone to hack on.
Print with 0.2mm layers to make sure the internal gaps print properly.
The bottoms of the 4 leafs print directly on the table and can be seen in the 4 slots in the bottom. To keep the leafs from breaking free during printing, I added 4 thin tabs attaching each leaf bottom to the outer ring. Use a razor blade or hobby knife to cut away these tabs.
The outer sphere is actually a dial that rotates. To free it, stick a small screw driver in the gap above the base ring and gently pry it free, working around the whole perimeter. Depending on how good your printer is with small gaps, you may need to insert a thin blade into the gaps at the top to free the leafs.