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    Default servo smoothing

    Hi All,

    I do have 3 axis hiwin ac servo setup on my mill. I have deskcnc board with the servos running in step dir . hiwin servos has a smoothing parameter from 1 to 500. machine runs smooth with any setting from 1 to 500 "but" circles are not circles when interpolating the higher the smoothing factor i chose the more it goes off. i can only get a real circle when the smooting parameter is set to 0 but the machine shakes a lot.
    i think the only way out is to have a real closed loop system ie . closed loop on the controller or software.
    does any of you use smooting on the servo drive parameter in a semi closed loop?and what is the accuracy you get when interpolating circles.

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    Default Re: servo smoothing

    Quote Originally Posted by fogassa View Post
    Hi All,

    I do have 3 axis hiwin ac servo setup on my mill. I have deskcnc board with the servos running in step dir . hiwin servos has a smoothing parameter from 1 to 500. machine runs smooth with any setting from 1 to 500 "but" circles are not circles when interpolating the higher the smoothing factor i chose the more it goes off. i can only get a real circle when the smooting parameter is set to 0 but the machine shakes a lot.
    i think the only way out is to have a real closed loop system ie . closed loop on the controller or software.
    does any of you use smooting on the servo drive parameter in a semi closed loop?and what is the accuracy you get when interpolating circles.
    Closed loop will only help if you have a mechanical problem like backlash Etc, what is the Encoder PPR you are using I believe they have 17 Bit Encoders so should work well, this is what has an effect on how smooth a machine will run, if you are not using the full 17 Bit's and have selected lower than the 17 Bit with Parameter changes

    Do they have autotune for these drives, so make sure you are using the full 17 Bit Encoder and do a Autotune if they have it

    Mactec54


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    Default Re: servo smoothing

    thank´s
    i´m using 2000 ppr encoders. that is close to 0.001 mm per step move. yes it has something like auto tune but i still have to mess with some parameters to fine tune it.
    if using the smoothing parameter it loses the capability to move 2 or 3 axis in sinc . like when machining a circle or a bore.



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    Default Re: servo smoothing

    when i say the machine shakes a lot is because i get hard stop on corners when using gcodes from cam programming. it gets better when using the smooting parameter but than circles are not circles anymore something like 0.1mm out of round.



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    Default Re: servo smoothing

    Quote Originally Posted by fogassa View Post
    thank´s
    i´m using 2000 ppr encoders. that is close to 0.001 mm per step move. yes it has something like auto tune but i still have to mess with some parameters to fine tune it.
    if using the smoothing parameter it loses the capability to move 2 or 3 axis in sinc . like when machining a circle or a bore.
    2000 PPR is way to low for a smooth operation jerk will always be a problem with such low count Encoders, you want the full 17 Bit that they offer then you will have a smooth running machine it has very little to do with the resolution
    0.001mm per step move

    The smoothing parameter is only to help any vibration resonance in your machine, this will not help much with the smoothing of the motion

    Mactec54


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    Default Re: servo smoothing

    Thank you again,
    i guess i´ll have to replace the encoders soon then.



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    Default Re: servo smoothing

    Quote Originally Posted by fogassa View Post
    Thank you again,
    i guess i´ll have to replace the encoders soon then.
    What control are you using Machine Software you may be able to change some of the Parameters that will help with how your machine runs

    Mactec54


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    Default Re: servo smoothing

    I´m Using deskcnc, had a try with mach3 but the problem is the same with both software. had another try today and got to the coclusion that circles are like egg shape tilt at almost 45 degress, not quite 45 but almost maybe 30 degrees. something like 0.05mm bigger at this angle than from the circle quadrant. it does not matter that i have the smooting on or off but the higher the smoothing factor the more it gets out of shape.
    i´m suspecting it has more to do with servo gain miss match maybe the velocity is not quite right , i try to mess with servo gain tomorrow.



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    Default Re: servo smoothing

    Hi,
    I had the acceleration to low on the servo protection tab, so it was slowing down one of the axis when milling a circle and messing the circle dimensions.
    now I have the smoothing on at 100 and it works nice very nice and smooth and dimensions are just right, not really it is more like 0.01 out of round. but for a old machine it is just fine. also the encoder 8000 counts after quadrature is just fine it works nice at 0.00125 mm axis resolution.
    Just to let you know.



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    Default Re: servo smoothing

    Quote Originally Posted by fogassa View Post
    Hi,
    I had the acceleration to low on the servo protection tab, so it was slowing down one of the axis when milling a circle and messing the circle dimensions.
    now I have the smoothing on at 100 and it works nice very nice and smooth and dimensions are just right, not really it is more like 0.01 out of round. but for a old machine it is just fine. also the encoder 8000 counts after quadrature is just fine it works nice at 0.00125 mm axis resolution.
    Just to let you know.
    Pleased to see that you are up and running, just imagine how smooth it would be with the 20Bit encoder if you think it is smooth with what you have then you are happy, the Resolution you are using has nothing to do with how the motors will perform

    Mactec54


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