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IndustryArena Forum > OpenSource CNC Design Center > Arduino > Poor output from Arduino CNC Shield v3
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  1. #1
    Join Date
    Aug 2015
    Posts
    3

    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


  2. #2
    Join Date
    Dec 2007
    Posts
    2134

    Re: Poor output from Arduino CNC Shield v3

    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
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

  3. #3
    Join Date
    May 2015
    Posts
    1422

    Re: Poor output from Arduino CNC Shield v3

    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.

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