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Thread: Laser won't cut a perfect circle

  1. #1
    Join Date
    Apr 2013
    Location
    Tennessee
    Posts
    145

    Laser won't cut a perfect circle

    The ends meet, and it's close, but not perfect. In fact, it's noticeable if you give a second look! How can I adjust this thing to get a bit more toward a real circle.

    Shenhui Laser
    RDWorks software
    Hobby Laser - 1800 X 1300 dual tube Shenhui (100 and 80W)

  2. #2
    Join Date
    Oct 2004
    Location
    Cape Town, South Africa
    Posts
    3,922
    Use the lead in and lead out setting , this basically starts and ends the circle beyond the actual circle and provides a circular cut without notches
    Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
    Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
    Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
    6 x longtai lasers 400x600 60w , 1 x longtai 20w fiber
    2x Gravo manual engravers , Roland 540 large format printer/cutter. CLTT setup
    1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher

  3. #3
    Join Date
    Mar 2011
    Location
    Olalla, WA
    Posts
    1,532
    That's due to backlash. You may find better results when the cut point starts/ends at different points on the circle.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  4. #4
    Join Date
    Apr 2013
    Location
    Tennessee
    Posts
    145
    I'll try to figure out what Rodney is talking about but I believe I can do what Rich suggests right away...maybe not....
    Hobby Laser - 1800 X 1300 dual tube Shenhui (100 and 80W)

  5. #5
    Join Date
    Mar 2011
    Location
    Olalla, WA
    Posts
    1,532
    To experiment with different start points you would use the node edit tool, select one of the nodes and then break it apart. That way when you rotate the circle the endpoint rotates along with it. If you don't break it apart then it may not affect where the laser begins to cut it.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  6. #6
    Lead-in/lead-out is aka tangential entry/exit.

    This is a cut path with lead in/out:




    the cut starts at the tip of the arc, which passes the first/last point, then upon completion, the path continues beyond the first/last point in the second arc...

    The idea is for your tool, knife, plasma flame or laser beam to never be stopped at the first/last point, and ideally leave an invisible transition...
    It works wonderfully when vinyl cutting with a swivel-knife machine, this insures the first/last point will be cut, which really helps with weeding.
    I've never actually tried it with laser cutting, I don't do very much high-def vector cutting...

    None of my laser's software or drivers have this function (that I know of), my old Casmate created the above...
    ========================================
    ELEVEN - rotary cutter tool machines
    FOUR - CO2 lasers
    THREE- make that FOUR now - fiber lasers
    ONE - vinyl cutter
    CASmate, Corel, Gravostyle


  7. #7
    Join Date
    Apr 2013
    Location
    Tennessee
    Posts
    145
    Thanks Guy's! Give me a day or two to work on this and if I fix it I'll get back here and say so. The darn thing is pretty close as it is....
    Hobby Laser - 1800 X 1300 dual tube Shenhui (100 and 80W)

  8. #8
    Join Date
    Mar 2014
    Location
    Iowa USA
    Posts
    4,441
    I have owned and used two laser engravers, never had to do this on either. My CNC plasma cutter, yes.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

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