Have you took a look at the emachineshop software? While it's main function is to provide a file for them to machine you a part via CNC, it does have an export function to get dxf files, and also STL file for 3D work.
http://www.emachineshop.com/machine-shop/Exporting/page295.html
I've not used it, but am thinking of playing with it some.
Ken H>
http://www.emachineshop.com/machine-shop/Exporting/page295.html
I've not used it, but am thinking of playing with it some.
Ken H>