Showing G53 coordinates

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22 Aug 2021 00:10 #218363 by phillc54
Replied by phillc54 on topic Showing G53 coordinates
The work coordinates are persistent and would be saved in the linuxcnc.var (parameters.txt inconverted PlasmaC configs) file in the config directory.
linuxcnc.org/docs/devel/html/gcode/overview.html#_parameters

There is no facility in QtPlasmaC to view them at the moment. I don't see it as too much of a problem to make them available as I believe it is available in the QtVCP infrastructure.

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22 Aug 2021 00:56 #218370 by beefy
Replied by beefy on topic Showing G53 coordinates
Fantastic Phill, thanks for the info.

Keith

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22 Aug 2021 01:27 #218371 by beefy
Replied by beefy on topic Showing G53 coordinates
Just came across a thread about a power failure scenario:

www.forum.linuxcnc.org/10-advanced-confi...c-var-file-from-code

Quote:
The file "linuxcnc.var" normally contains a string of numbers... all the offsets, etc. But apparently... when you make changes... they are written in MEMORY... not the file... UNTIL you tell it to quit. If power gets interrupted... and you open "linuxcnc.var" it is a blank file.

So if this is still the case with Lcnc then for complete protection, one would need to at least write down the machine co-ordinates at the work zero offset position, or take a photo of the screen. That is for a power failure or PC brainfart scenario, where Lcnc would not close down properly. My guess is limit trips and estops would not be an issue as that would not affect the var storage in memory.

Keith

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22 Aug 2021 09:35 #218387 by tommylight
Replied by tommylight on topic Showing G53 coordinates
See "position file", or last position or similar, LinuxCNC can save last position in case of power outage.
QtPlasmaC can also do that, we have plenty of outages here and it works perfectly.

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22 Aug 2021 10:49 #218401 by beefy
Replied by beefy on topic Showing G53 coordinates
Thanks for the info Tommy.

I did a bit of Google searching on the POSITION_FILE= something.txt

Based on the documentation and others chat on using it, I don't see how it could work to enable you to keep the exact position after a power outage. Here's my reasoning:

An axis could coast some distance after a power outage, especially if the machine was doing a rapid travel or cutting thin material at fast speed. As someone on a forum thread mentioned, the machine must be shut down properly for POSITION_FILE to keep the exact position.

I would envisage that even an estop or limit trip (if step pulses to the drive stop) at rapid speed would see the axis coast some distance too, and that would cause a discrepancy between the POSITION_FILE value and the actual axis position.

So it sounds good if the axis was stationary when the loss of power, or limit trip, etc happened, and the axis did not move until Lcnc was restarted, but as far as I can see, it would not be accurate for anything else.

That's why I always focus on the individual offset(s) even photograph the screen. The axis can be anywhere after shutdown, the PC can disintegrate, etc. As long as I don't move the material, once I'm up and running again, I home, move in absolute co-ords to the work offset position, zero the work offset, and I'm exactly back in position (within the accuracy of my home switches that is, which is within a few hundreds of a mm).

Very happy to be corrected if there's something I'm not understanding.

Keith

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22 Aug 2021 11:01 #218404 by phillc54
Replied by phillc54 on topic Showing G53 coordinates
Keith,
This widget looks like it will do what you want.
We would just need to find somewhere to deploy it.

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22 Aug 2021 22:44 - 22 Aug 2021 22:46 #218444 by beefy
Replied by beefy on topic Showing G53 coordinates
Sorry Phill but there's no widget attached to the post.

Ha ha, I had to Google what a widget is in Lcnc. I really am back at the beginning.

Keith
Last edit: 22 Aug 2021 22:46 by beefy.

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22 Aug 2021 22:56 #218446 by phillc54

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23 Aug 2021 00:03 #218450 by beefy
Replied by beefy on topic Showing G53 coordinates
Thanks heaps Phill, that's fantastic.

Just spent over 50 mins searching Google for python solutions. Pulled a few hairs out by the end LOL.

Time to learn how to use Qtvcp widgets.

Cheers,

Keith

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23 Aug 2021 02:27 #218454 by phillc54
Replied by phillc54 on topic Showing G53 coordinates
From what I have observed whenever you set a WCS coordinate it is immediately saved in the parameters file so anything in the parameters that is listed as Persistent shouldnt be affected by power loss etc.
linuxcnc.org/docs/devel/html/gcode/overview.html#_parameters
You can check by opening the parameters file in Geany or similar then changing coordinates and you will see the file is changed immediately.

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