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IndustryArena Forum > Hobby Projects > Hobby Discussion > A circle, a simple circle. How hard can it be?
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  1. #1
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    A circle, a simple circle. How hard can it be?

    I'm new to CNC having built a 2-axis plotter driven by Arduino, CNC-Shield and GRBL 1.1.

    I can draw a square.

    I now want to draw a circle and have failed miserably for days.

    I have googled on and off for about a week now and looked at dozens of examples. Not one of them does a circle. Not on my machine nor in any of about 5 different simulators I've tried. At best a limp arc, at worst straight lines or nothing.

    Come on.

    A circle.

    Could someone post the GCode to do say a circle centered at X=0,Y=0 with radius 5cm?

    Since I now believe it is impossible. Please check your work here:
    GCode Simulator
    or here:
    https://nraynaud.github.io/webgcode/

  2. #2
    Community Moderator ger21's Avatar
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    Re: A circle, a simple circle. How hard can it be?

    G0 X0 Y5
    G2 X0 Y5 I0 J-5

    Doesn't work in the first simulator you linked, but works in the second one.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
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    Re: A circle, a simple circle. How hard can it be?

    Hi, if you took the time to learn G code all will be revealed, but you gotta be in it to win it.
    Ian.

  4. #4
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    Re: A circle, a simple circle. How hard can it be?

    Quote Originally Posted by ger21 View Post
    G0 X0 Y5
    G2 X0 Y5 I0 J-5

    Doesn't work in the first simulator you linked, but works in the second one.
    Yeah... doesn't work on my machine (running GRBL).

    The first command works but the circle doesn't and I get:
    error 33 for G2 X0 Y5 I0 J-5

  5. #5
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    Re: A circle, a simple circle. How hard can it be?

    OK, the circle code works in UniversalGCodeSender but not in GrblController 3.6.1

    I thought these programs just send GCodes to the machine so how can they get different results??

  6. #6
    Community Moderator ger21's Avatar
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    Re: A circle, a simple circle. How hard can it be?

    Different controls read g-codes differently.
    I think that GRBl doesn't allow full circles, only partial arcs.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  7. #7
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    Re: A circle, a simple circle. How hard can it be?

    But GRBL is on my Arduino - I'm just switching between different PC software which both send "G2 X0 Y2 I0 J-2"

  8. #8
    Community Moderator ger21's Avatar
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    Re: A circle, a simple circle. How hard can it be?

    I think that Universal G Code Sender breaks the circle up, and sends multiple arcs to GRBL.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  9. #9
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    Re: A circle, a simple circle. How hard can it be?

    I think I see what's happening. If you're in relative mode (G91) you can't draw circles.

    FAIL:
    >>> G91
    >>> F100
    >>> G0 X0 Y2
    >>> G2 X0 Y2 I0 J-2
    ok
    ok
    ok
    error:33

    SUCCESS
    >>> F100
    >>> G0 X0 Y2
    >>> G2 X0 Y2 I0 J-2
    ok


    Is there any way to just draw a circle centered from wherever you are?

  10. #10
    Community Moderator ger21's Avatar
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    Re: A circle, a simple circle. How hard can it be?

    I think I see what's happening. If you're in relative mode (G91) you can't draw circles.
    You can, but the code is different.

    G91
    G0 X0 Y2
    G2 X0 Y0 I0 J-2
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  11. #11
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    it's really hard for me

  12. #12
    Different controls read g-codes differently.
    I think that GRBl doesn't allow full circles, only partial arcs. It sounds very hard buy have you tried looking for it in the Internet& There are a lot of tutoriels there.
    https://writings-centre.com/buy-coursework-online.html

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