There are many different software that can be used to design this simple puzzle. The most simple being, the free to download, Google SketchUp. I have experience with Autodesk Inventor Pro so that was the 3D program I chose to use. Start by choosing a plane to sketch on. I choose the flat x plane to sketch on. Next I took the general idea from Google Sketch Up and sketched it into Inventor. I then completed the sketch and turned it into a drawing form and gave it all the proper dimensions. Also in this form it is easier for someone to figure out exactly how big or small to make each piece.
Step 1: Extrude and Export
Now that you have finished your drawing you can use the extrude feature to make it the height that you want. The original design calls for it to be a half an inch tall but I will later show you how to scale it down in the next step. Once you have got your final piece you can save and export your file. Most 3D printer programs require a .STI file so export your piece as that.
Step 2: Plugging in to 3D Printer Program
My 3D printer is the Makerbot Replicator 2x and comes with the makerbot desktop software. To place your piece in the program go to file then click add and chose the saved .STI file. make sure the piece is on the platform and extruding out of the correct extruder. Next to scale down your piece go to scale on the side and make it the dimensions you want it to be. My final pocket sized one was 2'' tall 1'' wide and 1/4'' tall. Some settings you may need to change to have optimal printing. The extruder tempature should be 230 degrees C and the bed of the 3D printer should be 130 degrees C. Once these are all correct you are ready to save the .thing file and take it to your 3D printer.
Step 3: Print Time!
Now insert the SD card with the .thing file on it and find your piece. Once the printer is all preheated it will start printing. My print time for my puzzle with my dimensions took about 40 minutes which is not too long. One the print is all complete you can remove your pieces from the bed. Note: it is extremely important to remove the rafting from your print otherwise the pieces will not go together properly!
Step 4: Finished Puzzle and Thoughts
Now you have a finished puzzle that can fit in your pocket and keep you from boredom for hours! After a couple of tries you should figure it out. If not then give it to a family member or friend to try out and see if they can solve it. That's the end of this instructable, if you have any questions, concerns, or comments please feel free to comment below. All feed back is appreciated.