I am finishing up a 3d printer build where mach3 will be used to control the unit
with the G code being written by Slic3r.
 A axis will be used to drive the  pellet fed extruder head (.375 dia. 20 to1 L/D 3 to 1 comp.).
I can determine output of plastic with regard to turns of the screw.
Is there a site or group where I can get a detailed explanation on how to setup A axis in Mach3
and Slic3r?

Thank you
Johnd