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Arc segments cutting as circles!

Discussion in 'SketchUcam Bugs' started by agfrag, Feb 20, 2017.

  1. agfrag

    agfrag New Member

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    Well, I used to use SketchUcam a few years ago, then started with BobCadCam, and recently came back to SketchUcam to cut a double bass bridge template. After my drawing was complete, I used the inside and outside cuts only, SketchUCAm had no problem with the edges, looked real good. Up pops the GCode Plotter, and everything looks good.

    Now it gets weird...

    I take the code over to my Mach3 CNC program, and load it. All the arcs are now full circles! I've got a zillion circles all over the Toolpath window, and I'm thinking hmmm, that's weird. So just for the heck of it I, step through the code without running the code and watch the toolpath progress. Well, the tool shows that the code is only following the section of the circle that would logically make up the arc. Then it jumps to the next circle, completes the next subsection of that circle to complete the arc and so on.

    So I figure, Ok, maybe it's just a visual tracking/display thing, where somehow each arc segment is displayed as a full circle, and only the necessary subarc is used to move the tool. So I load a piece of scrap, and run it, and Lo! ...unlike when I stepped through the code, now it is actually cutting each and every full circle!

    I am stymied. Attached are my SketchUp Make and Gcode .cnc files.

    Any help would be greatly appreciated!
     

    Attached Files:

  2. 3DMON

    3DMON Moderator Staff Member

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    Recently Sketchucam is now using incremental mode for arcs which Mach3 does not like so you will have to use these instructions to make Sketchucam work with Mach. This info is in the help file.

    arcmoveij() is INCREMENTAL mode.
    • the 'incremental' form of IJ is used so make sure you set your controller to incremental mode by issuing G91.1
    • Setting or un-setting this does not change the actual Gcode, arcs are ALWAYS incremental mode, this setting just tells the controller what to expect.
    • you can add this code to the G-code via the Options menu
    • an option to output G91.1 as part of the Gcode header has been added to the Feature Options menu.
    • GPLOT will NOT like this option and will not display the plot. You should rather set your controller to default to this mode.
     
  3. swarfer

    swarfer Moderator Staff Member

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    'does not like' well , that is not the right phrase (-:
    and SketchUcam has always used incremental mode when it used IJ for large holes/countersinks/counterbores.
    The new aspect is using IJ for all arc segments.

    There are 2 modes for arc IJ usage, absolute mode and incremental mode. Mach3 'likes' them both and your Gcode can use either mode, it can even use both modes in the same file! (so long as they are preceded by the correct mode switch code).

    I have updated the front page of the help to mention that if the controller is in the absolute mode it might draw HUGE CIRCLES and also mention Mach3 in relation to this.

    So now users only have to RTFM to solve this (-:
     
  4. 3DMON

    3DMON Moderator Staff Member

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    Yeah I guess I worded that wrong. :facepalm:
     
    swarfer likes this.
  5. agfrag

    agfrag New Member

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    Thanks 3DMON and swarfer for the reply and clarification. G91.1 solved my issue! :)
     
  6. alexeiv

    alexeiv New Member

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    What do you mean with "RTFM", I dont understand?
    I have de same problem and just to review the g code with camotics
     
  7. 3DMON

    3DMON Moderator Staff Member

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    It means read the manual...lol.
     
  8. swarfer

    swarfer Moderator Staff Member

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    RTFM is Read The Flipping Manual
    go here http://swarfer.github.io/sketchucam/
    and search for 'huge'.

    Camotics is not a good previewer as it is way too permissive of incorrect code.
    However it still needs to know what mode to show arcs in so your code needs a G91.1 in the header to tell it to use incremental mode.
    Most controllers default to incremental mode but if there is any doubt about the mode then your code needs to set it.

    You can try this viewer
    https://ncviewer.com/
    or this
    https://planet-cnc.com/
    (yes I know it is supposed to have hardware, but the software by itself is an excellent previewer)
    or this
    http://nc-corrector.inf.ua/index_EN.htm
     

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