Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:39919.
I am proud to present a new Printable Interlocking Puzzle Cube, but this time I didn't design it.
Following the release of PIP#2, I was contacted by Bram Cohen (puzzle designer and author of the BitTorrent protocol) asking whether I had found any printable interlocking puzzle cube designs with a level higher than 1, i.e. needing more than a single move to take the first piece out.
This sounded like a great challenge and I set about about trying to design one but then Bram beat me to it - not once but twice. As Bram commented in his email, " the main thing causing difficulties is that the printed bottom of the pieces can't be facing the outside directly, because then they can just be pulled off as the first move, but because the bottom must by definition have the most voxels, putting those on the interior makes it very hard to fill up all the external voxels and not stuff shut the internal voxels."
His first attempt was a level 2 puzzle cube but that was quickly superseded by this very clever level 4 design.
If you like this puzzle and fancy an extra challenge, perhaps you would consider paying just £3 for my latest and best design from here https://www.etsy.com/uk/listing/831851235/digital-files-for-printable-interlocking
EDIT: (23/12/2014) Thanks to a great piece of work by mateddy (see http://www.thingiverse.com/thing:569118) I can finally make this puzzle available in OpenSCAD format.
EDIT: (12/10/2019) Congratulations and thanks to David Gontier who has now beaten the record with a level five design.