3D Printing Puzzle Pen

Here's a cool 3D printing project. In this instructables, I'll show you how I made an awesome puzzle pen using 3D printing.
3D Printer: Dremel
Filament: PLA
Modeling Application: 123D Design Desktop ( get from: http://www.123dapp.com/design )
Draft the Design

Draw out the draft design and puzzle pieces.
Modeling

Modeling the pieces in 123D Design Desktop following you design draft.
Note: You must design the teeth using same dimension. And test the clearance, 0.1mm maybe so tight, it is so hard to pull out the pieces for me. So, I used 0.2mm clearance, it is easy to pull out.
Print Out

Print them out. According to the length of the cartridge, print body pieces repeatedly. You also can print with different colors.
Assembling

Complete the puzzle by assembling all the pieces.