Raspberry Pi 4 with Mesa 7c81

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05 Apr 2021 23:06 #204983 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
The machine does not lose position.

It is not exactly repeatable in that it does not do the same thing each time but it does do something at the same location of the pass if you are making multiple passes to say cut a part out. I’ll try to get an example picture

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05 Apr 2021 23:15 #204987 by andypugh
My first thoughts are that the 7C81 is too "dumb" to do this.

I assume that the backplot does not show this?

There are many possibilities, including mechanical. Check that all your couplings are tight. Though it doesn't feel like a max-force point or a max-speed (backlash) point.

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05 Apr 2021 23:20 #204988 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
Definitely not mechanical. It is obvious when watching it that it is commanded motion...

You can see in this photo what it has done after multiple passes. Not exactly in the same spot but same type of error.

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05 Apr 2021 23:21 - 05 Apr 2021 23:26 #204989 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
When you say it does not lose position, are you saying
the tool returns to the correct path after the deviation?

Maybe a simpler test code would help diagnose the issue

What are your min_ferror and ferror settings?
large values of these can mask steggen setup errors


Posting your hal and ini files would also help
Last edit: 05 Apr 2021 23:26 by PCW.

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05 Apr 2021 23:22 #204990 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
And correct backplot does not show it. Also verified on standalone gcode simulator
Attachments:

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05 Apr 2021 23:29 #204991 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
I wrote a simple gcode program to test. It was a rectangule with rounded corners I used g02 for the curves. Again, perfect plot on screen but the issue you saw in the first photo labeled “A”

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05 Apr 2021 23:34 #204993 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
I will look up the configs in just a minute as well post the gcode I ran for the rectangle

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05 Apr 2021 23:51 #204997 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
Ferror= .5
Min_ferror= .05

Will post both .Hal and .ini

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05 Apr 2021 23:54 #204998 by andypugh
I agree that it looks like a command motion (even on the part) but if it does not show up on the backplot then I _think_ that can only be backlash comp (bad backlash comp).

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05 Apr 2021 23:59 #205001 by JohnG
Replied by JohnG on topic Raspberry Pi 4 with Mesa 7c81
I would agree except that I created the rectangle specifically to make the motors run in only one direction throughout the curve (x only moving in the negative direction and y only moving in the positive direction) to eliminate backlash as the culprit. I really do not believe it is backlash or backlash comp (which is set to zero anyway)

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