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GRBL mystical z axis movement while moving x + y axis together

Discussion in 'Control Software' started by thuni, Feb 8, 2016.

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  1. thuni

    thuni New
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    Hello everyone,

    I am facing a strange problem on my DIY CNC project. I can move every axis one by one, without any unexpected bahaviour, but when I move the x axis and y axis at once, my z axis is moving too. I can not figure out why.
    Some lines about my setup. I am using an Arduino Uno together with 2 Big Easy drivers (for x + y) and a smaler Easy driver for z axis. Motors are standard Nema 23 and Nema 17. I wrote a little G-Code for testpurpose only and this behaviour occures even when I test the motors without my machine (disassambled).
    G-Code:
    M3
    G21 (All units in mm)

    G00 X25.000000
    G00 Y25.000000
    G00 Z25.000000
    G00 X0.000000
    G00 Y0.000000
    G00 Z0.000000
    G00 X25.000000 Y25.000000
    G00 X0.000000 Y0.000000

    The last two lines cause the Z axis to turn fast and followed by vibration and then turn again. I already double (tripple) checked all connections. I dont have a clue, since the first lines turn the expected motors only.

    I hope someone has an idea. If further informations are needed i will try to hand them in later (like grbl config -> defaults)

    thanks in advance
    thuni

    Edit: I forgot to mention the software... Grbl version is 0.9j and I am working with UniversalGCodeSender v1.0.9. I also tested bCNC with the same results.
     
  2. Sonny Jeon

    Sonny Jeon Veteran
    Staff Member Moderator Builder

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    This sounds like a grounding and electrical noise problem. Make sure to 'star ground' your stepper drivers and Arduino, if you can. Also, try removing any external sources of electrical noise to rule these out.

    Secondly, does Grbl report back the correct positions over the course of the short g-code program? If it does, that means that Grbl is outputting the step pulses correctly, because Grbl tracks actual position from counting the step pulses and their directions. If not, then there's something else wrong. Maybe settings.
     
    David the swarfer likes this.
  3. thuni

    thuni New
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    Wow, thanks for that info. I desoldered the GND cable from the driver board (z axis) and resoldered the connection with a new cable. Now everything is working fine. Btw. grbl reported only those movements which were send to the arduino. So for the last lines of the code only movement for x and y were reported, so in software everything worked fine.
     

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