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Thread: Circles not round, 6040 laser machine

  1. #25
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    Default Re: Circles not round, 6040 laser machine

    Before, I will try a bigger square, a lot more than 10x10 cmts...
    Martin.-



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by otromar View Post
    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.-
    it´s curious because that's the next idea i had planned haha, will try and report back

    Last edited by tigox; 04-20-2016 at 06:22 AM. Reason: mistake


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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by Christian_S View Post
    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.
    hum... out of ideas regarding the way to test it, any crude method leaves me without knowing if i have wrong steps per pulse or if i have backlash :/



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by tigox View Post
    hum... out of ideas regarding the way to test it, any crude method leaves me without knowing if i have wrong steps per pulse or if i have backlash :/
    What I suggested earlier would tell you if the steps per units are correct. That is, you take a tape measure and using as much length of your axis, command the X-axis to move the distance.
    You can adjust the pulses per unit steps to match the distance. The longer your distance the less error due to "eye-balling" the start-end marks.
    Do the same for the other axis. Since the movement is in one direction, the backlash will be a very small percentage of error over the long length of your measurement.

    Backlash is perhaps better sensed if you manually rotate the motor shaft so that you can perceive the amount of motor shaft rotation with no movement of the axis. This will be small.



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by tigox View Post
    hum... out of ideas regarding the way to test it, any crude method leaves me without knowing if i have wrong steps per pulse or if i have backlash :/
    The solution is to measure the difference between "inside" and "outside" features in line with the axis, that are programmed to be cut out with identical size/distance. As the absolute size of the features should be the same, the difference can normally be attributed to backlash. The exception is if your axis response is non-linear to the instructed position, this can be checked by measuring if there is any difference between identical features cut at different positions along the axis. I have sketched an example of cut outs you can do to measure backlash this way:



    If you follow this method the backlash on the axis parallel to the cutouts will be the difference divided by four ((y1 - y2)/4).

    Edit: The sketch is in millimeters, but the sizes are not critical other than enabling easy measurement with a caliper.

    Attached Thumbnails Attached Thumbnails Circles not round,  6040 laser machine-20160420-png  


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    Today I made many... MANY tests, and noticed some interesting things.
    Firstly I tried switching the X axis for the y axis aaand the circle came out mirrored which is... Interesting?
    Tried changing the microstepping and nothing.
    Tried changing the current on the X axis which interesting enough is half of the y axis?
    Tried many squares and circles and came to the conclusion that above a certain size the circles seem to come out straight.
    Tried screwing all screws.

    Etc etc... I tried many things today and don't know what to think of the results, if anyone has any idea of what this tells me, I would be grateful, especially the circles coming out oval but mirrored when I exchanged the connectors on the stepper drivers.
    I'll attach all tests I made today, and be aware that rectangles and alongated things are due to me having different steps at one point causing one of the axis to go a greater distance.

    ALSO, I noticed a 0.2mm difference between the X and y axis when I made a square. The y axis cut was 0.2 mm shorter than the X axis, but I don't think this would cause such an irregular circles especially diagonal errors like what's happening.

    Attached Thumbnails Attached Thumbnails Circles not round,  6040 laser machine-img_20160420_204042-jpg   Circles not round,  6040 laser machine-img_20160420_204039-jpg   Circles not round,  6040 laser machine-img_20160420_204029-jpg   Circles not round,  6040 laser machine-img_20160420_204025-jpg  



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    Default Re: Circles not round, 6040 laser machine

    Hi Tigox,

    I just posted a similar issue here: http://www.cnczone.com/forums/genera...ml#post1871682

    If I can fix my problem (or vice versa), perhaps we can help each other out.

    Thanks,
    Mike



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    Default Re: Circles not round, 6040 laser machine

    i wrote without read carefully. edited
    Martin.-

    Last edited by otromar; 04-20-2016 at 11:07 PM.


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    Default Re: Circles not round, 6040 laser machine

    I wrote something but is wrong.
    I ask you, when you invert the axis and say mirrored, mean ... rotated 90° ? if is rotated 90° then i think this is not a problem to the axis, is a problem of software or controller...
    Martin.-

    Last edited by otromar; 04-20-2016 at 11:10 PM.


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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by trdcelica View Post
    Hi Tigox,

    I just posted a similar issue here: http://www.cnczone.com/forums/genera...ml#post1871682

    If I can fix my problem (or vice versa), perhaps we can help each other out.

    Thanks,
    Mike
    of course!



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    Default Re: Circles not round, 6040 laser machine

    Quote Originally Posted by otromar View Post
    I wrote something but is wrong.
    I ask you, when you invert the axis and say mirrored, mean ... rotated 90° ? if is rotated 90° then i think this is not a problem to the axis, is a problem of software or controller...
    Martin.-
    by mirrored i mean mirrored on the y axis, for example, if you made a circle on an acrylic piece and then flipped the acrylic piece to its back you would observe the same effect



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    Default

    Pics of what's happening.
    Left is after switching wires between x and y and right is normal state of the machine

    Attached Thumbnails Attached Thumbnails Circles not round,  6040 laser machine-img-20160421-wa0004-jpg  


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Circles not round,  6040 laser machine

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