Stepper Motors Oscillating

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16 Sep 2020 20:03 #182462 by tjones
I have been noticing lately that when I am running at the higher end of machine travel I am getting oscillation in my stepper motors. I have only seen oscillation on the Servo side of things when they aren't tuned right. When I turn down my max speed it doesn't happen as much. It will even happen when I am just jogging, say to touch off a tool all of a sudden it is oscillating. It doesn't seem to effect the positional accuracy as I have measured a position before/after oscillation and its the same. I never saw this kind of issue with my last control setup (Parallel BOB). I can only think it has something to do with the initiation files I recently upgraded to using a 7i76E with the latest version of LinuxCNC. I did config through PNCCONF with only minor changes to get my spindle VFD working. When running a open loop system, should there be any values in the PID sections?

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16 Sep 2020 20:30 #182466 by PCW
Replied by PCW on topic Stepper Motors Oscillating
Can you post you hal and ini files?

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16 Sep 2020 20:33 #182467 by tommylight
Edit the hal file and omit or remove the lines with
setp pid.x.maxerror .0005
or similar for each axis, see if that gets rid of oscillations.

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18 Sep 2020 23:34 #182691 by tjones
Replied by tjones on topic Stepper Motors Oscillating

File Attachment:

File Name: Tosh-Mill.hal
File Size:10 KB

File Attachment:

File Name: Tosh-Mill.ini
File Size:4 KB


Files are attached
Attachments:

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19 Sep 2020 03:28 #182701 by PCW
Replied by PCW on topic Stepper Motors Oscillating
I cannot see anything obvious wrong
Can you plot the following error in halscope?

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02 Aug 2021 18:14 #216722 by tjones
Replied by tjones on topic Stepper Motors Oscillating
I changed my settings to comment out the pid.x.maxerror line and that fixed my oscillation issue. The problem I get now is I get "Joint 0 following error." It is not all the time and this last time it did it I checked the line it ended on and it was only and X Y direction it was a simultaneous XYZ movement, which I though might be the issue. I can re-run the same code and it will fail at different points.

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02 Aug 2021 19:00 #216732 by tjones
Replied by tjones on topic Stepper Motors Oscillating
Reading a few other posts it looks like there is some things that setting FERROR and MIN_ERROR can help by setting these correctly. I am not sure I have ever rally touch the FERROR and MIN_ERROR as I have never had issues with them. On all three axis is was set to .5 and .05. I decided to increase just the X axis to .5 and .5 and that tool went all over the place. So I set the X axis back to .5 and .05 Then I tried .5 and .06 on the Y axis and then I got a following error on Joint 1. I think I only ever had a following error on Joint 1. It seems like making MIN-ERROR larger I get more issues. After reading the manual on this it looks like this is the setting that will physically slow down the feed rate in order to hit the projected path. I also use G64 all the time with P.001. What is the relationship between G64 and MIN-ERROR? I mainly use the G64 because it makes the motion bath so much smoother and significantly reduce the burning in the corners I get from wood.

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02 Aug 2021 21:34 #216751 by PCW
Replied by PCW on topic Stepper Motors Oscillating
Can you post your current hal/ini files?

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02 Aug 2021 23:28 #216755 by tjones
Replied by tjones on topic Stepper Motors Oscillating
Files below.  I was going to try uncommenting the setp pid.x.maxerror .0005 line and reduce my MIN_FERROR to something smaller and see if that does anything. 

 

File Attachment:

File Name: Tosh-Mill_...8-02.hal
File Size:10 KB
 

File Attachment:

File Name: Tosh-Mill_...8-02.ini
File Size:4 KB
Attachments:

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02 Aug 2021 23:48 #216757 by PCW
Replied by PCW on topic Stepper Motors Oscillating
None of those PID max error settings should cause oscillation

The ferror settings only set the threshold for shutdown
from a following error. If you get a 0.05 inch following error
something is really wrong.

Do you ever get latency errors?

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