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Are my OX CNC GRBL Settings wrong?

Discussion in 'CNC Mills/Routers' started by Brayden DeVito, Nov 13, 2014.

  1. Brayden DeVito

    Brayden DeVito Well-Known
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    Hey guys,

    I just built an OX CNC, and i'm having some issues getting the GRBL (0.9) settings correct.

    I followed the same settings on KRAMs build page for step size, etc.. but i'm getting really slow and choppy movement. All of the components are from the official ox parts list.

    What are some tips to calibrate the GRBL correctly?

    I noticed if the feed rate is faster, the machine moves way more smoothly...
    slow movements are really choppy and rigid.....

    Any help would be appreciated..

    Thank you!
     
  2. Robert Hummel

    Robert Hummel Custom Builder
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    What voltage are you running your OX at and what drivers?
     
  3. Brayden DeVito

    Brayden DeVito Well-Known
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    Thanks for the reply!

    I'm running a 24V 30A Power Supply.
    Plus.. StepStick Kit (4pcs) A4988 Stepper Driver

    Brayden
     
  4. Robert Hummel

    Robert Hummel Custom Builder
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    Ok so if I understand this correct then your using the same nema23 motors on open builds store, so that means your under powering them as your peak amps for the stepsticks are 1.8 amps and the motors require 2.8

    Lower your voltage to 14 volts if ya can and give that a try :)
     
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  5. Brayden DeVito

    Brayden DeVito Well-Known
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    Hold on.... So I ordered the wrong pololu drivers? Would these be more suitable for a nema 17??

    Without lowering the voltage on the power supply, what are my options?

    I don't want to underpower the steppers.. Thank you so much!

    Not to mention.... Lowering the voltage would mean less power on the 23s right?
     
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  6. Robert Hummel

    Robert Hummel Custom Builder
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    No current has to do with power of the motor voltage helps with speed
    Even the high end polo drivers can only put out 2 amps with heatsinks and cooling
    Yes nema 17 are better on polo's
     
  7. Brayden DeVito

    Brayden DeVito Well-Known
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    Okay, so it sounds like my polo driver board isn't the right choice for the OX.

    Lowering the voltage to 14V would fix the choppiness on the steppers? I'm trying to mill aluminum, so I want as much smooth power as I can get.

    Excuse my inexperience, but what is the best driver for the OX? In order to get the most accuracy and power out of all 4 motors..
     
  8. Robert Hummel

    Robert Hummel Custom Builder
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    On my fiber OX I'm using nema23 and stepsticks that run @ 14.5 volts and it runs smooth as silk even @ low ipm
     
  9. Brayden DeVito

    Brayden DeVito Well-Known
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    OK, so I need to lower the voltage of my power supply.

    How does this effects the amount of amps going to each stepstick?

    It sounds like I need drivers with more amp delivery..? Where does voltage come into play during this?

    I'm learning a lot from this thread thank you so much!
     
  10. Robert Hummel

    Robert Hummel Custom Builder
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    Volts and amps are two different things but can be confused easy.
    Lowering your voltage will simply allow your power supply to provide more amps.

    If you have let's say 24 volt 30 amp and where to turn it down to 12 your rated amps would be 60 amps.
    That's off topic though lol

    When it comes to stepper motors your best to provide them with the rated amps and increase voltage to smooth out speeds
     
  11. Brayden DeVito

    Brayden DeVito Well-Known
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    Okay I get it.

    What I don't get is how is 30 amps not enough to power the drivers?

    I get that the motors will be underpowered, but adding more amps does what to the choppiness of the steppers? It seems like there is enough amps.. Ha sorry...

    What GRBL settings are you using for your step sticks? I can try to duplicate your settings and see what it does!

    Thank you so much!
     
  12. Robert Hummel

    Robert Hummel Custom Builder
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    Has nothing to do with your power supply, I use 14.5v and stepstick current set at max, heat sinks and a cooling fan
     
  13. Wieslaw Olszewski

    Wieslaw Olszewski Well-Known
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    Bryden DeVito I have same problem about smooth movement.
    Do you sorted your problem?
    Could you help me to? please!!!
     
  14. Wieslaw Olszewski

    Wieslaw Olszewski Well-Known
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    Could you help me about same problem?
     
  15. David the swarfer

    David the swarfer OpenBuilds Team
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  16. Wieslaw Olszewski

    Wieslaw Olszewski Well-Known
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    I look tomorrow.
    Thank you
     
  17. Wieslaw Olszewski

    Wieslaw Olszewski Well-Known
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    I was look now thos link and I not anderstand nothing about this.
    I'm new user, I never before use cnc.
    I neede someone who tell me step by step what to do, please
     
  18. Serge E.

    Serge E. Master
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    Looks like we have it under control now (through FaceBook chat and video calls).

    It was mostly the issues I was having when I first started :
    • setting X and Y maximum rates high enough for rapids to be rapids
    • keeping the steppers powered at all times instead of using a delay between moves
    • adjusting the potentiometers on controller to feed steppers enough power
    • ...
    Then tweaking steps to get proper travel from all axis.
     
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  19. Wieslaw Olszewski

    Wieslaw Olszewski Well-Known
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