tinyg small circle with flat side

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  • February 17, 2019 at 2:46 pm #11310
    gazingm42
    Member

    I have a cnc system which uses the thread rods, 2 Y motors, x motor and z motor. All connected with
    the coupler with 2 set screws between the motor and threaded rod. Using vcarve desktop and tiny g.

    I been using it for about 2 years or so cutting 100’s of projects.

    I was making a project cutting a few small 13mm holes in a piece of wood using 1/4″ end mill bit. Each of the holes cut with a flat side. I adjusted the speed rate and direction etc but still get the issue.

    After reading on the internet. I checked the backlash which seem to be ok. Even replaced them with spares.
    I checked the coupler set screws and re-tighten them.

    Too be honest in all my projects this is the first small circle I have done, so I never noticed the issue.
    It seems to be where the bit enters the circle to start the cut. I slow down the feed rate and plunge rate
    into the cut as well.

    I thinking a issue with the tinyg no translating it correctly

    February 17, 2019 at 2:58 pm #11311
    cmcgrath5035
    Moderator

    My initial guess would be you are experiencing a variation of what is usually referred to as the “arc issue”. Is the hole coded as a 360 degree arc (aka circle) or multiple segments that total 360 degrees?

    The easiest solution is often to regenerate your gcode in MM, rather than inch. Another option is to have your gcode generated without arcs, so circles will be all short segments.

    I am assuming your tinyG $fb is 440.20

    February 17, 2019 at 3:10 pm #11312
    gazingm42
    Member

    I should have mention that I use exclusive mm in every setting.

    I will need to check my version of tinyG. I have perform no software in 18
    months.

    February 17, 2019 at 3:21 pm #11313
    gazingm42
    Member

    here the simple Gcode its using.

    G90
    G17
    G21
    G0Z1.000
    G0X0.000Y0.000
    M3 S12000
    G0X53.184Y65.175Z1.000
    G1Z-3.200F127.0
    G3X57.509Y69.500I0.000J4.325F381.0
    G3X53.184Y73.825I-4.325J0.000
    G3X48.859Y69.500I0.000J-4.325
    G3X53.184Y65.175I4.325J0.000
    G1Z-6.400F127.0
    G3X57.509Y69.500I0.000J4.325F381.0
    G3X53.184Y73.825I-4.325J0.000
    G3X48.859Y69.500I0.000J-4.325
    G3X53.184Y65.175I4.325J0.000
    G1Z-9.600F127.0
    G3X57.509Y69.500I0.000J4.325F381.0
    G3X53.184Y73.825I-4.325J0.000
    G3X48.859Y69.500I0.000J-4.325
    G3X53.184Y65.175I4.325J0.000
    G1Z-12.800F127.0
    G3X57.509Y69.500I0.000J4.325F381.0
    G3X53.184Y73.825I-4.325J0.000
    G3X48.859Y69.500I0.000J-4.325
    G3X53.184Y65.175I4.325J0.000
    G1Z-16.000F127.0
    G3X57.509Y69.500I0.000J4.325F381.0
    G3X53.184Y73.825I-4.325J0.000
    G3X48.859Y69.500I0.000J-4.325
    G3X53.184Y65.175I4.325J0.000
    G0Z1.000
    G0X86.812Y68.989
    G1Z-3.200F127.0
    G3X90.637Y65.164I3.825J0.000F381.0
    G3X94.462Y68.989I0.000J3.825
    G3X90.637Y72.814I-3.825J0.000
    G3X86.812Y68.989I0.000J-3.825
    G1Z-6.400F127.0
    G3X90.637Y65.164I3.825J0.000F381.0
    G3X94.462Y68.989I0.000J3.825
    G3X90.637Y72.814I-3.825J0.000
    G3X86.812Y68.989I0.000J-3.825
    G1Z-9.600F127.0
    G3X90.637Y65.164I3.825J0.000F381.0
    G3X94.462Y68.989I0.000J3.825
    G3X90.637Y72.814I-3.825J0.000
    G3X86.812Y68.989I0.000J-3.825
    G1Z-12.800F127.0
    G3X90.637Y65.164I3.825J0.000F381.0
    G3X94.462Y68.989I0.000J3.825
    G3X90.637Y72.814I-3.825J0.000
    G3X86.812Y68.989I0.000J-3.825
    G1Z-16.000F127.0
    G3X90.637Y65.164I3.825J0.000F381.0
    G3X94.462Y68.989I0.000J3.825
    G3X90.637Y72.814I-3.825J0.000
    G3X86.812Y68.989I0.000J-3.825
    G0Z1.000
    G0Z1.000
    G0X0.000Y0.000
    M30

    February 17, 2019 at 3:35 pm #11314
    gazingm42
    Member

    tinyg [mm] ok>
    tinyg [mm] ok>
    [fb] firmware build 440.20
    tinyg [mm] ok>
    tinyg [mm] ok>

    February 17, 2019 at 6:13 pm #11315
    cmcgrath5035
    Moderator

    I sort of figured you were mm, because you said a 14mm hole.

    Your code seems to cut the holes as four separate segments, maybe each 90 degrees.

    I have not other suggestions aside from try without arcs.
    The typical arc failure have been when very slight arcs (very large I or J parameter) which accentuates math rounding errors. the fundamentalis 8 bit math. But your arcs have rather tame values of I and J.

    If you want to play with it a bit, try this:
    In your CAD tool, rotate your entire part by something like 25 degrees relative the the x,y coordinate system.
    Then regenerate gCode.
    I am curious if circles will still be 4 arcs with this sort of pattern
    ….
    G3……I0.000J….
    G3……I…J0.000
    G3……I0.000J….
    G3……I…J0.000
    ……

    just hacking it now….

    February 18, 2019 at 8:59 am #11316
    Gaylord
    Member

    I am assuming nothing else about the machine has changed. My only advice is to remove all grease and oils from the lead screws and the nuts by using a solvent like acetone. Brush on some acetone while running the axes to get the residue from the nuts. Use a stiff brush and lots of rags to get everything clean. Before lubricating with WD40 run each axis back and forth several times one at a time. Listen to any changes in the sound during travel. try running the program the program. If this works you were probably missing steps. If this doesn’t help try adjusting your acceleration settings.

    On my machine, I found when hand turning each axis I could feel binding along the way in different spots. The fix after much frustration was replacing the lead screws with ball screws and more powerful steppers on the X and Y Axes.

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