Z axis moves in the wrong direction

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  • July 22, 2012 at 5:16 pm #3380
    xMishka
    Member

    Hi,

    I got a Grbl shield as part of my CNC kit from Shapeoko and I am having some issues with my Z axis and am wondering if the shield is the culprit. My X and Y axis don’t have any problems but the Z axis commands sometimes turn the stepper in the wrong direction even thought the commands are the same.

    Example:
    G91
    X10 X10 X10 X10 – All commands move in the same direction
    X-10 X-10 X-10 X-10 – All commands move in the opposite direction of the above
    Y works the same way.

    Z10 Z10 Z10 Z10 – Some move up some move down.
    Z-10 Z-10 Z-10 Z-10 – Some move up some move down.

    I am running the grbl08_basic GRBL code with preset settings for my CNC machine. I ran the Z axis with a drill a few times to smooth it out so it doesn’t bind and so it moves freely. I tried changing the speed on the Z axis. I tried messing with the pots a bit (I didn’t change them much since I can’t find any docs on how to set them). I am not sure what else I could do. Could it be a defective Grbl shield or motor?
    Any help is appreciated.

    Thanks,
    -Victor

    July 23, 2012 at 7:50 am #3387
    alden
    Member

    Victor,

    Thanks for registering at the forum. Your questions handled one-by-one:

    – Here is a link about setting the pots. They are one turn pots so *please do not turn them more than 270 degrees* or they will break. However, I doubt the pot settings are your problem, so I wouldn’t mess with them right now. Just set them in the middle of the range.

    https://www.synthetos.com/wiki/index.php?title=Using_the_grblShield#Setting_Motor_Current

    – I’d like to confirm that you (1) have the kit from Inventables and that (2) your grblShield has the Z axis mod. Does your board have the little wire to the switch like the one in the last picture on this page? (scroll all the way down)

    https://www.synthetos.com/wiki/index.php?title=Z_Axis_Mod_for_Shapeoko

    – If it does not let me know. Can you please post your grbl settings? Z should not be more than 1200 ($3=1200), and might possibly need to be set to less, depending on the friction in your system.

    – Check the Z axis motor plug. DOes this give good contact? If any 1 of the 4 wires does not contact or contacts intermittently then it could cause what you are seeing.

    – If you swap motors – i.e. put the Z motor on Y and the Y motor on Z – what happens? This may be hard to do given that the motors are in the machine – you may need to remove the Y belt and/or change the grbl settings. Does Z work OK and Y have problems, or the other way around?

    Please let me know how this goes.

    • This reply was modified 12 years, 3 months ago by alden.
    July 26, 2012 at 4:18 am #3395
    xMishka
    Member

    Hi Alden,

    Thanks for the quick reply. I got my kit from Shapoko.com and my Grbl shield has the Z axis mod. Below are my settings and what I tried.

    Settings:

    $0 = 43.74
    $1  = 43.74
    $2 = 300
    $3 = 30
    $4 = 500
    $5 = 1000
    $6 = 0.10
    $7 = 28
    $8 = 25
    $9 = 0.05
    I checked the connectors and wiring to make sure everything was connected securely and correctly.

    I swapped the X and Z axis connectors on the Grbl shield and ran some commands after changing $2 to 43 so it didn’t hit the end of the axis and  the motor moved in the correct direction each time.

    I swapped the connectors back and tried changing $3 higher and lower and the Z axis is still having the same issue.

    I also tried changing $2 higher and lower.

     

    Considering that the X axis motor worked fine on the Z axis I am thinking that it may be the Z axis motor. Any thoughts?

     

    Thanks.

    July 26, 2012 at 6:29 am #3396
    alden
    Member

    Let me make sure I understand correctly. You moved the X motor to the Z axis board connector. You changed $2=43.74. You sent a “Z” command like G0Z10 to the board and the Z channel drove the X motor and X axis just fine. Do I have that right?

    Second, when you swapped the X and Z motors did you also run X commands with the Z axis motor and axis ($0 should have been set to 300)? Did that work OK too, or did the motor still behave erratically?

    Third, when you moved the motors back to their original configuration the Z axis was still having problems.

    It sounds like the Z connector or possibly the Z motor itself is bad, especially if it was unable to be driven from the X channel (if you did that second test). The board sounds like it’s fine.  If you have not done the Second test, can you do that as well to confirm?

    July 27, 2012 at 12:11 am #3408
    xMishka
    Member

    Yes. The Z channel on the board drives the X axis motor correctly however the X axis channel on the board did not drive the Z motor correctly. It had the same issue. Same command being sent consecutively made it move up and down so I am pretty sure it’s the motor. I have checked and rechecked all the connections and everything is connected well. I will see if I can get it warrantied since it is brand new. Thanks for the troubleshooting tips. Your help is much appreciated.

    -Victor

    August 9, 2012 at 11:27 am #3418
    Riley
    Keymaster

    Did you get it working?

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