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Uno and CNC shield issues

Discussion in 'Controller Boards' started by Jones, Nov 18, 2018.

  1. Jones

    Jones Well-Known
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    Running an clone Uno and Cnc shield with Nema 23's rated for 1.05A with shielded 22/4 cable drained to ground on a 24v 350W power supply. Drivers are clone DRV8825, vref 0.5. Spindle is a Makita trim router. Have also tried this setup with a Bosch 1617 with the same result.

    Motion is good on jogging, and during linear and arc tests with G0 and G2 manually input strings. All axes test good.

    Using UGS and Openbuild's own Gcode sender. Fusion 360 for modeling and CAM, which, aside from manually removing any tool commands, seems to work ok.

    Computer is an AMD a6 based HP laptop. Have tried both 1m and 6m USB cables with no change in performance.

    The problem is, when running programs, I get random errors and random times during the program. Very simple 2d and 2.5d programs seem to work reasonably well, but if they last longer than 6 minutes, it just takes off into the workpiece and gouges a line in a generally relative positive and z negative position. Controller usually throws an error, though sometimes it doesn't and I have to emergency stop to keep it from crashing.

    I thought this was a shielding issue, and it marginally improved from adding shielded cable on all axes, but that might be just the way I feel about it rather than supported by data.

    Does anyone have any suggestions, because this is incredibly frustrating. The problem seems to increase with higher feed rates.

    I've thought about putting ferrite cores near the steppers and winding a shield on the router cord. Haven't tried that yet. Or switching to TB6600 drivers.

    Any ideas?
     
    #1 Jones, Nov 18, 2018
    Last edited: Nov 18, 2018
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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  3. Jones

    Jones Well-Known
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    2 fans. Driver heat sinks are always cool to the touch.

    edit. z axis driver is warm, but not hot.
     
    #3 Jones, Nov 18, 2018
    Last edited: Nov 18, 2018
  4. Jones

    Jones Well-Known
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    Well, I moved one of the fans closer to the drivers and I'm getting more errors not less. I think it's interference from the fans, and maybe the proximity of the power supply. I don't know. Will be doing more tests this week.
     
  5. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    As a thought, you might take a look at the solder joints.
     
  6. Jones

    Jones Well-Known
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    I think the Uno needs to be shielded from the drivers, as they're basically choppers, so emi bleedover might have a significant effect. I have some leftover thermal pad as well, so a shield with a thermal pad would act as a good sized heat sink. That I can do. Then a shield over the top to pick up stray square waves from the drivers, all bled out to ground.

    I'm probably wrong about this, but I'm going to give it a shot while I have everything apart.
     
  7. Jones

    Jones Well-Known
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    Checked the continuity on all the cables. No cold joints. Ordered some ferrite clips.
     

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