Simplified 3d will not run extruder
To use Mach3 to send printing you need to define the extruder as A instead E, since Mach3 only drives X,Y,Z,A and B motors. you can see an explanation here on is possible to send printing with mach3? Question. 

I haven't tried to see if is possible to change this letters directly on 3D simplify, because i'm using ramps 1.4 instead the CNC driver control. But there is an ADDON to slice your gcode with Mach3 called gnexlab, try to find it on google search. I've downloded few years ago.

Added Link 
gnexlab Addon