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  1. #13
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    Default Re: Circles not round, 6040 laser machine

    all suggestions the manufacturer gives me are software based as most chinese manufacturers...
    i hope it's not a physical problem with the machine... do i even stand a chance in fixing this? the oval shape is noticeable on smaller circles and as you go bigger it becomes less noticeable, wouldn't it be the other way around if it was a physical problem?



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by tigox View Post
    i have tried about 10cm (4 inches) and it was short by about half a millimeter ( about 0.019685 inches), and this happened on both axis ( not surprisingly since they have the same steps per pulse unit) thus that doesn't seem to be the problem because it would not show as much on such small circles.... :/
    That's good.
    I'm trying to eliminate the calibration as a source of error.

    The next thing I would want to know if making a circle real slow also causes an error. In other words, is the error affected by speed? Or feedrate/acceleration/inertia... type issues.
    Is there a some flex in the X / Y axes that might cause this error?



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    Quote Originally Posted by KOC62 View Post
    That's good.
    I'm trying to eliminate the calibration as a source of error.

    The next thing I would want to know if making a circle real slow also causes an error. In other words, is the error affected by speed? Or feedrate/acceleration/inertia... type issues.
    Is there a some flex in the X / Y axes that might cause this error?
    Changing speed or acceleration makes no difference at all, which tells me that it's not caused by flex? I think...



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by tigox View Post
    Changing speed or acceleration makes no difference at all, which tells me that it's not caused by flex? I think...
    If it is really not mechanical (including back-lash), then one would look at the software, including configuration settings, side for possible errors.

    Your circles, or rectangles, g-code looks good on the monitor?



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    Quote Originally Posted by KOC62 View Post
    If it is really not mechanical (including back-lash), then one would look at the software, including configuration settings, side for possible errors.

    Your circles, or rectangles, g-code looks good on the monitor?
    I don't think the problem is backlash because the problem happens no matter the speed or acceleration.
    Lasercut doesn't show gcode.



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    Default Re: Circles not round, 6040 laser machine

    Have you tried different software then? Mach3 (which usually is shipped with the 6040 machines) or perhaps LinuxCNC?



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    Default Re: Circles not round, 6040 laser machine

    have you try to reduce speed ?



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    Quote Originally Posted by javanree View Post
    Have you tried different software then? Mach3 (which usually is shipped with the 6040 machines) or perhaps LinuxCNC?
    Didn't know Mach3 or linuxcnc worked with mpc6585, would not mind trying if so.

    - - - Updated - - -

    Quote Originally Posted by philippelang View Post
    have you try to reduce speed ?
    Yes both high and low (and veeery low speed haha)



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    Default Re: Circles not round, 6040 laser machine

    It looks to me like simple mechanical backlash, on both axises. Since backlash is most noticeable when changing direction on each axis with backlash, it does fit with the squarelike circles seen in your pictures, since direction changes where the circle is perpendicular to the axises. (The circles may look oval because the diameter is reduced in the axis directions.) Backlash could also explain why it is more visible for smaller circles, since the deflection would be larger in relation to the circle diameter. Excessive backlash can also cause straightness error in movements perpendicular to the axis with backlash.

    As you have mentioned tightening the belts, I would try backlash compensation in software if that is an option, and also to try cutting any straight lines at an angle to the machine axises. If this does not help I would probably start looking for a mechanical upgrade.



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    Quote Originally Posted by Christian_S View Post
    It looks to me like simple mechanical backlash, on both axises. Since backlash is most noticeable when changing direction on each axis with backlash, it does fit with the squarelike circles seen in your pictures, since direction changes where the circle is perpendicular to the axises. (The circles may look oval because the diameter is reduced in the axis directions.) Backlash could also explain why it is more visible for smaller circles, since the deflection would be larger in relation to the circle diameter. Excessive backlash can also cause straightness error in movements perpendicular to the axis with backlash.

    As you have mentioned tightening the belts, I would try backlash compensation in software if that is an option, and also to try cutting any straight lines at an angle to the machine axises. If this does not help I would probably start looking for a mechanical upgrade.
    How might I go about testing backlash? Lasercut does in fact have backlash compensation



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    Default Re: Circles not round, 6040 laser machine

    The normal method of measuring backlash is to use a dial or test indicator like this. If you don't have a suitable indicator some cruder method can be devised, or you can just try adding a little bit of compensation and experiment.



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    Default Re: Circles not round, 6040 laser machine

    Hi, to discard errors of one axis in the controller, can you invert the conections between controller and drivers ? (with all the precautions about homing, distances of x and y etc)
    Just thinking
    Martin.-



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