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I need some help...

Discussion in 'CNC Mills/Routers' started by BismarckDon, Sep 11, 2015.

  1. BismarckDon

    BismarckDon Well-Known
    Builder

    Joined:
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    I finally got a little time to work on my CNC machine.

    I'm trying to get the Grbl configuration settings entered, and I'm struggling.

    I found a site on the internet ( http://noblesque.org.uk/ShapeOko/grblcalc/ ) and was trying to work through the calculations. At this point, I have removed all step jumpers on my CNC Xpro controller board. Here is some specific information about my machine: It's modeled after the Open Builds OX design with an overhead gantry. I'll be running a Dewalt DWP 611 1/4" router.
    X and Y axis belt / pulleys: GT3 20 tooth 18.3 mm diameter
    Z axis: 8 mm Acme rod: 1.25 mm / revolution
    Nema 23 stepper motors on X, Y and Z axis (2 on Y axis)



    I do not have limit switches or homing switches installed yet. (Approx. working bit area is X=560mm, Y=380mm, Z=70mm)

    Here are my current Grbl config settings:
    $0=10
    $1=255
    $2=0
    $3=6
    $4=0
    $5=0
    $6=0
    $10=3
    $11=0.020
    $12=0.002
    $13=0
    $14=1
    $20=0
    $21=0
    $22=0
    $23=1
    $24=25.000
    $25=500
    $26=250
    $27=1.000
    $100=3.333
    $101=3.333
    $102=160
    $110=635.000
    $111=635.000
    $112=635.000
    $120=100
    $121=100
    $122=100
    $130=560
    $131=380
    $132=70

    Obviously, I don't know exactly what to do. I can get the x axis to move, but not sure about the scale or accuracy yet. It seems to move slow and almost choppy. I suspect my settings are incorrect. No luck with Y axis.

    Can anyone give me a little assistance?

    Thanks!

    Don
     
  2. Joe Santarsiero

    Joe Santarsiero OB addict
    Staff Member Moderator Builder

    Joined:
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    Hey bismark,
    Travel per revolution is going to be the pitch diameter (not the pulley diameter) × pi.
    Ex. a 19.000mm pitch Dia. >> 19.000mm x pi = 59.690mm per rev.
    So. a stepper with 200 steps per rev.
    59.690mm/200=.298mm per step.

    Running the same stepper in half step will yield a resolution of .298mm/2= .149mm per half step.

    and so on for 1/4 and 1/8 step settings.

    The z is easy. 1.25mm/200 or 400 or 800 and so on.

    While I don't have time atm,
    I'm sure someone will stop by to help you with all of the grbl settings. If not I will later. There are some grbl posts with setting here on the forum and the grbl wiki is handy as well.

    Joe

    Edit. There may be a number floating around that tells what to add to the pulley tooth pitch diameter to figure out the belt pitch diameter as a shortcut, but I don't have that. plus there are different manufacturers for these belts.
    Gates is the main source of this design I'd read through their material first.
    http://industrialbeltdrives.com/wp-content/uploads/2012/05/20099_POWERGRIP_DDMANUAL_ENGISH.pdf
     

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