Another option for gear creation can be found at
www.gear2motion.com. Not free though (looks to be up to $120). You might recognize the creator of it, Art Fenerty, who was heavily involved in the creation of the well known hobbyist CNC software Mach3. Though admittedly have not played with much and has a learning curve to pick up it does seem to have a bunch of tricks up its sleeve. I think he initially created for making clocks but appears to have abilities to do many other things like pulleys, bearings, different gears types, bolts/nuts, ect and create .STL files for printing. I used to create a couple of timing gears for printing a while back and they came out good. I might have to play with again a little this weekend if get time..
If need free and software in above post not doing for ya I am thinking I had seen a gear generator for SCAD somewhere but can't seem to find. Maybe a in-depth search of Thingiverse would bring up.
Just a FYI for another possible options to check out.
JS