When I was designing timing belt wheels for Thierry (SumoBot).
I was searching for a DXF generator, but the only thing I could find was a parametric pulley generator for 3D objects on thingiverse.
I edited the openSCAD code to output DXF’s you can find it here: Parametric Pulley DXF generator.
For more information on how to use it: check out my instructable.