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  1. #41
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    Default Re: SBL Magnaturn Retrofit

    It should do, but any decent servo drive should have a reasonable tolerance to noise.

    I'm assuming the suspect drive, is still suspect when driving a different axis, where another drive is functioning ok?
    If it is, I'd be sending it back to DMM.



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    Default Re: SBL Magnaturn Retrofit

    Hi m_c,
    I connected my scope last night and got no ripple at all on the 24vdc power supply. Still need to check my 5 and 12vdc.

    Yes i have done several tests. Which include testing each drive with both axes. And the drive in question(zaxis) will show the same issues when connected to X axis servo. The X axis drive has no issues, or at least none that i can tell during tuning, running the heavier Z axis.

    Right now iam going back and forth with support from DMM to eliminate any possible noise issue. As they believe this is causing the problems of tuning with Kmotion. But i have also noted that when using there AutoTuning software the Z axis drive always comes up with way lower settings,gains,accel and such. But the X axis drive does not.

    So while iam waiting on some filters for the main power input to drives iam double checking things.

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  3. #43
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    Default Re: SBL Magnaturn Retrofit

    Anyone know how an encoder can have a Z index with only 4 wires in the encoder cable?
    Troy

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    Default Re: SBL Magnaturn Retrofit

    Quote Originally Posted by Need TECH Help! View Post
    Anyone know how an encoder can have a Z index with only 4 wires in the encoder cable?
    Troy
    The encoders are not your typical 5v pulse encoders, they are a little smarter. I think 2 wires are used for power and the other two are used to communicate with the drive, i think it might be a serial connection. They are absolute encoders so the drive knows exactly where the motor is at all times and even as soon as it powers up, so dont really need an index. I think the guys from dmm said something about other info being sent from encoders too, like motor temp. Seems pretty slick. I like the idea of it being absolute, even if something messed up with noise for an instant it still knows exactly where it is.

    I found the DMM tuning to be poor at best. Best results I had by far was with analog control in torque mode which is the only way to completely bypass the DMM tunning. The DMM signal ground (not same as chassis ground) needs to be connected to kanalog as well. I missed this and lost position when spindle was started.



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    Default Re: SBL Magnaturn Retrofit

    I added filters to the Main Servo power and added a filter to the output of the 24VDC power supply as suggested by DMM. Also scoped the 5 and 24VDC supply outputs and got no ripple at all. After making these changes the plots and issue has not changed with this one drive. Any suggestions?

    Troy

    Attached Thumbnails Attached Thumbnails SBL Magnaturn Retrofit-plot-gif  
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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    I'm confused. The attached plot is different from the attached data.

    SBL Magnaturn Retrofit-unknownplot-png

    Are they of the same axis in different modes? What are the settings and data for both?

    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    Hmmm, thats is a previous one. Dont know how... Will do again under a new name.

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    Default Re: SBL Magnaturn Retrofit

    Tom,
    Here is data under a new name. Dont know how that other plot got in there.

    Attached Thumbnails Attached Thumbnails SBL Magnaturn Retrofit-zaxis3-jpg  
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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    That must be with the drive in Step/Dir Position mode?

    That looks reasonable to me. After the move the Output correction returns to near zero so not likely any loss of Step Pulses to the Drive.

    Peak position error 22 counts on initial startup (stiction?) Typical error ~10 counts. I don't know what resolution or speeds this relates to.

    Looks like position errors would be ~ 50 counts greater if running the Drive open loop without KFLOP making corrections because the Output is ~ 50 counts during the move.

    SBL Magnaturn Retrofit-troyzerror-png

    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    Yes it is CL Step/Dir. What is the output shape at the end where it goes up and down?Seems very odd.
    But, if i continue to test moments like this i end up with growling of motor during movement and a plot that is like what you got in previous post. I get big position errors. To the point where axis returns about 1/2" short of start. And just continually gets worse.
    Also what causes the green output to be so rough looking? Is this just because of the mechanics of machine?

    Thanks
    Troy

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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    The ramping up down at the end is where the motor is dithering +/- 1 encoder count is fairly normal. It is a bit abnormal that to correct 1 count of error KFLOP has to tell the drive to move 10 counts before it moves.

    Such noisy looking plots are normal. It is caused microscopic mechanical vibrations and such and mostly unavoidable.

    The other plot shows KFLOP needing to make corrections of a thousand or more steps to get the encoder to read the correct value. That means a large number of steps to the drive were lost or encoder counts from the drive were lost. I don't know why it would work sometimes and sometimes not. Did it "growl" when that previous plot was made?

    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    No the growling isnt noticed until axis starts to really mis the return position. Before it gets extreme the axis will gradually return past the starting point by about .001" after each test movement. I have noticed that having the drive resolution set lower gets more constant results. But i dont have these issues with the other drive(xaxis) running the Z axis.

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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    When you are swapping out the drives are you only swapping out the drive and are all cables unchanged?

    Before it gets extreme the axis will gradually return past the starting point by about .001" after each test movement.
    I don't really understand what that means.

    The "bad" plot you sent earlier is so big that the end of the motion back to the start is not shown. It would be nice to see what happens at the end in order to see if KFLOP's Output returns to near zero or not.

    You might also make open loop moves to see if the drive still has problems doing that.

    Regards

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    Hi Tom,
    I have done both and get the same results.
    When a test move in Kmotion is executed, the axis returns back to where it started but overshoots by .001" each time the test is ran.

    Such noisy looking plots are normal. It is caused microscopic mechanical vibrations and such and mostly unavoidable.
    You reminded me that i wanted to change my ball screw mount design on Z axis. This should take out some of that noisy plot.
    Will be a couple days before i will be testing again.
    Thanks,
    Troy

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    Default Re: SBL Magnaturn Retrofit

    Hi Tom,
    Reworked my fixed ballscrew support for Z axis, which was also the cause of the .001" over shoot i was describing above. A nut came loose allowing the ball screw to move. But now iam getting much better results and can test again.Here is a plot after mount rework.
    Can you remind, what part of the plot graph should i look for the amount of error?
    And the axis never stops dithering after a test move by one count. Unless i disable ,zero, and enable. Sometimes have to do this procedure a few times before it will stop.
    This plot is using the Z axis Drive on the Z axis. This drive is the one that has been acting differently than the other on X axis. Right now iam letting it sit idle and will test move again. Usually movement and response would start getting worse after axis is powered on and sitting for an hour or 2.
    Now iam back to where i left off. And back to electrical noise trouble shooting. As per DMM i have installed filters on the Main Power to drives and on the output of my 24VDC supply. If all goes well and the issue has been fixed i will be trying analog again.

    Thanks again,
    Troy

    Attached Thumbnails Attached Thumbnails SBL Magnaturn Retrofit-zaxisdriveclstep1000-jpg  
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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    The error in that plot would be the difference between the red and blue plots. But on that scale you can't really see the difference. So change the Plot Type to Position Error, Output vs Time.

    Why do you think you have a noise problem?

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    Hi Tom,
    That much i understand/remember, what i was talking about is when looking at the Plot Position Error, is the amount of error measured the difference in the height of plots when zoomed in or is it at the 0 scale on the left of screen ?
    The noise assumption came from DMM when i told them what was happening with the one drive missing steps at high resolution and growling.

    Troy

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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    hat much i understand/remember, what i was talking about is when looking at the Plot Position Error, is the amount of error measured the difference in the height of plots when zoomed in or is it at the 0 scale on the left of screen ?
    The error (blue plot) uses the left scale. The output correction (green) uses the right scale.

    So in your plot you can see when the move begins the axis initially lags behind with an error of ~90counts. Then KFLOP makes a correction of ~100 steps and reduces the error toward zero.

    SBL Magnaturn Retrofit-poserr-png

    The noise assumption came from DMM when i told them what was happening with the one drive missing steps at high resolution and growling.
    Oh

    Regards
    TK http://dynomotion.com


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    Default Re: SBL Magnaturn Retrofit

    Ok. Update: After placing the filters on the Drives Main power input, problems appear to have been fixed. And also have the drives running in analog mode and tuned very well in Kmotion.
    Now iam working on the Z index pulse from drive output. I currently have the Z index connected to Kanalog JP2 Differential Inputs. When doing a test move by Step/Reponse window in Kmotion, shouldn't there be counts showing for the Z axis index on the Axis window? Currently iam not showing any counts for Z index on either X or Z axis.

    Troy

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    Default Re: SBL Magnaturn Retrofit

    Hi Troy,

    Now iam working on the Z index pulse from drive output. I currently have the Z index connected to Kanalog JP2 Differential Inputs. When doing a test move by Step/Reponse window in Kmotion, shouldn't there be counts showing for the Z axis index on the Axis window? Currently iam not showing any counts for Z index on either X or Z axis.
    I'm not sure I understand. But no, an Index pulse is usually a single signal pulse. It isn't A B quadrature and won't cause counts. It is usually a tiny pulse that will be hard to see by eye. Normally a C Program is used to detect it during the Homing process. See the SimpleHomeIndexFunction.c and SimpleHomeIndexFunctionTest.c examples.

    HTH

    Regards
    TK http://dynomotion.com


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