Poor output from Arduino CNC Shield v3

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

http://www.cnczone.com/forums/attach...d=294728&stc=1http://www.cnczone.com/forums/attach...d=294730&stc=1http://www.cnczone.com/forums/attach...d=294732&stc=1http://www.cnczone.com/forums/attach...d=294734&stc=1

Aside from the 24VDC power supply, and the use of very low power drivers, that combined may not be providing the amount of power needed for the steppers (what is the ratings of them?), the stepper itself is only supported along the two rear bolts, not ideal at all, I would be amazed if you don't get some movement there when the Z is moving.

The other thing to check is if the cutter is flexing, although it looks like you cut it with a larger Vee bit?

Also, have you checked if you have any binding anywhere that would cause a jerky response?

Missed steps, too fast feed rate, wrong settings, etc, are other possible reasons for what you're seeing.

Does the Z axis have any play, is the leadscrew supported by bearing blocks top and bottom, or just a bearing inserted into the frame? Etc, etc.

cheers, Ian

Yeah, could be the arduino board, could be the steppers, could be mechanical play.

Try this: zip tie a permanent marker to the clamp so it's reasonably rigid, set it up so it just drags the pen around lightly and wind your feed rates right back to something in the order of 100mm/min. If it looks good, it suggests that your arduino is interpreting correctly. Then speed it up to the run speeds you're using now. If it's still good it suggests that the arduino is coping at the speeds (not a timing problem). Then it's down to mechanical play in the machine and/or skipping steppers causing your problems.