Tutorial on how to design gears for 3d printing

Here is one of the many approaches to designing gears for 3D printing.
1) use Gear template maker to design a gear
2) export to a jpg file
3) use freeware wintopo to vectorize and save vector as a 3D dxf file
4) use a CAD program to import the 3D dxf and extrude surfaces
5) clean up with free netfab or send directly to 3D printer 

Notes:
This project explains how I go about making different types of gear profiles (different sizes, tooth number, addendum etc...).
The Gear Template Maker (GTM) shareware is a program that was designed for CNC or laser cutting of gear outlines but only generates a 2D dxf file. I wanted to get to a 3D dxf file that could be 3D printed on an Up!3D printer.
The steps that I use apply to sprocket gears, involute gears,rack and pinion gears.
The basic idea is to get from a jpeg image generated in GTM through freeware version of Wintopo to generate a 3D dxf file that you can extrude using any basic CAD program, then print on a 3D printer. The entire process should take under 3 minutes.

This video shows how to configure a sprocket gear that can be used with a Tamiya belt kit. See www/thingiverse.com project "Making gears".