G'day Lars
I am using
this parametric model available on Thingiverse. It allows design of 12 different tooth profiles but I have only designed GT2 pulleys on it.
In my case I use OpenSCAD to design the pulley, export the STL file, edit it in Sketchup (I know it is not the best but I know it well and don't have other CAD software), generate a new STL file in Sketchup and export it to the 3D printer software.
I have printed various pulleys for a 16" scope and for a Nexstar 11" mount (both ONSTEP conversions) and the pulleys are strong enough to handle the balanced loads. Slewing speeds up to 4 degrees per second. I have also printed pulleys for focusers and a rotator/de-rotator (light duty applications).
My biggest challange was to allow for shrinkage (tooth meshing on the outside) and to get the inner diameters to fit accurately on different shafts because it is almost impossible to accurately drill out the 3D printed pulley (pulley either wobble or the hole is off centre or you can't drill when using a D shaft). I also found that 24T GT2 pulleys is about my smallest pulley I can print with the ABS I am using. I have tried smaller but it didn't work with my setup.
On the heavy load pulleys I am using M4 grub screws where necessary (tap my own thread into a pre-printed hole). Usually 2 grub screws for a round shaft and one for a D shaft.
Bert