Hey, I'm new to all of this, but I recently converted my 3-axis Mach 3 CNC machine controller over to an Arduino with a CNC Shield v3, running 8825 drivers, so that I could utilize a 4th axis in order to run dual Y-axis motors (one on each side of gantry). Everything seems to be working great, except that the output is less than desirable! My cuts look like the drawings of a 3 year old! I can't figure out what's going on. I've tried two different post processors, and various materials, and the results are the same each time. The entire process runs very smooth and quick, but the detail is horrible. Any ideas?

Hardware:
Arduino Uno
CNC Shield v3
4) DRV8825 drivers (X, Y, Z, A)
Axis Y and A cloned together.
4) Nema 23 motors
24V power supply
12,000 RMP quite spindle

Software:
CAD/CAM - Aspire 4.0
grbl hex 0.9a
grblControl 0.5.2 (https://github.com/Denvi/grblContol/)


Post processors used:
G-Code (mm) (*.tap)
G-Code (mm) Arcs (*.tap)

Thanks!

Mike