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CBeam jogs fine, runs gcode terribly, help please

Discussion in 'CNC Mills/Routers' started by hasemar, Jun 28, 2016.

  1. hasemar

    hasemar Well-Known
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    Hi, I have just built my first C, I posted my build . In there you can find a video of me testing the axis by jogging the x axis. It seems to be jogging just fine.

    However, I tried to run a bit of G-code that draws a 1 inch circle around the origin and ended up with a funky shape.

    Getting to this point for me was a monumental feat. The X and Y motors sounded like they were running very slow and almost sounded overloaded. (not that I really know what that sounds like)

    info:
    179in-oz 2.8A motors
    DVR8825 polulu drivers
    Rasp Pi with protoneer hat + arduino nano integrated
    using CNCv1 (GitHub - cheton/cnc: A web-based CNC milling controller for the Arduino running GRBL.) for grbl interface

    Basically I copy/pasted the g-code example from the grbl wiki into notebook and saved it as a .tcl file and then uploaded it to CNCv1.

    I'm lost... cant you tell.

    Anyone have any ideas one what I should be checking?

    Thanks in advance.
    Ryan
     

    Attached Files:

  2. Kyo

    Kyo Master
    Staff Member Resident Builder Builder

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    Hello Ryan,
    The G-code looks fine. I ran the circle-inch.gcode file in CAMotics without any problems. My first guess is skipped steps. When the motors skip steps the g-code keeps running thinking it should be in one spot when in fact the machine is still in another. Have you adjusted the current output on the drivers? both too little and too much current can cause skipped steps. I also find having a fan along with the heat sinks on the drv8825 drivers help. Those guys like to run hot. lol
     
    #2 Kyo, Jun 28, 2016
    Last edited: Jun 28, 2016
  3. hasemar

    hasemar Well-Known
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    Thanks for the fast reply Kyo.
    I checked out the driver datasheet, It looks like I can adjust the current output with the little potentiometer on each driver, right?

    It also says that the drivers can provide up to 2.2A, but the stepper motor has a max rating of 2.8A. Is this okay? What current output should I be shooting for?

    Ryan
     
  4. Kyo

    Kyo Master
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    Yes that is correct. When making adjustments small turns at a time then recheck. Current Limit = VREF × 2 If you want to run your motors at 2A set the drivers to a reference voltage of 1.0 V.


    I run my drivers with heat sinks and cooling fan at 1.8A. It looks like your motors are comparable. (mine are 175oz 2.8A ) so that should get you in the ball park.
     
    #4 Kyo, Jun 28, 2016
    Last edited: Jun 28, 2016
  5. hasemar

    hasemar Well-Known
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    I followed the video and turned my drivers down to vref = 1. I ran the circle g code again and it worked!

    Thank you very much for the help!
     
    Kyo likes this.

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