This Instructable is going to guide you through the critical steps to create a CAD file for 3D Printing a Cryptex. It will use Autodesk Inventor 2012, and will detail the critical steps needed to create it. Basic experience with your CAD software of choice is recommended. This should include creating parts, assemblies, extruding, cut extruding, revolving, embossing, and basic parametric modeling skills. If you are interested in making an exact copy of my Cryptex, please skip to Step 17, which details modifying my files to edit the combination.
IF YOU ARE CURRENTLY SEARCHING FOR, OR PLANNING ON SEARCHING FOR, THE GEOCACHE CRYPTECH (GC3K7QE); YOU SHOULD BE FOREWARNED THAT THERE ARE SPOILERS INCLUDED IN THIS INSTRUCTABLE.
POST-INTRO NOTE (PLEASE READ BEFORE COMMENTING): I have recently received many comments about getting the STL for printing. I don't believe you actually want the STL file. This Cryptex is a fixed combination, and thus, if I give you the STL, it will be exactly as shown in the images above. Plus, there is writing on the side which you do not need or probably want.
Second: This print requires use of a printer with a soluble support material. There is no way around it. Since the rings are printed on to the outer chamber with about a hundredth of an inch gap, and are inaccessible to clean out any non-soluble support material, you WILL need a printer that can print in a soluble support. I used a Stratasys uPrint printer, which prints in ABS and a support material.