Apparently Impossible Sphere

thingiverse

The seemingly impossible sphere puzzle is derived from the classic cube version. To create this unique design, STLs of an impossible cube were combined with a sphere. Print four "s1" and "s2" parts using a well-calibrated 3D printer (I recommend .3 height and 10% infill on my ToM). Post-print cleanup may be necessary to remove blobs. This puzzle offers a slightly increased challenge compared to the cube, as it cannot rest flat during assembly. If you find the provided size difficult to handle, consider scaling up your print. For open Scad source (compatible with both cube and sphere) and a tighter fit, check out this derivative: http://www.thingiverse.com/thing:25395. Note that if your printer is not calibrated, it's best to use the original design provided here.