Schoen I6 surface modeled in Rhino V5 and thickened in MeshLab. Approximate dimensions 65mm cubed, with a 1.4mm wall. Visit this link to find out more:

http://facstaff.susqu.edu/brakke/evolver/examples/periodic/periodic.html#I6

The surface creates a checkerboard-like pattern on the end faces, resulting in some serious overhangs. In order to print without generating support material, I modeled support faces that can be easily removed with an X-acto blade.

Modeled in rhino using approximate surfacing techniques. Thickened mesh created in Meshlab. The model with the suffix "_support" will print without needing to generate support material in your slicing program. Printed at 0.25mm layer thickness.