G92 messing up the coordinate

Hi,
I have no idea where to post this but here is my problem.
Open EMC, home X,Y,Z axis manually ( I run the machine without limit switches)
run one button auto Zero touch off, & execute the G code & everything runs like clock work.
The problem come when I the Z-touch off again & it shows the "exceed joint limit" in red letter bar at the bottom right corner of AXIS screen.

My idiot solution to that is to re-start a fresh session of EMC2 without incident.

I eventually isolated the problem to the use of G92. The X Y & Z coordinates will have a mind of its own & disregard what I type in the MDI command bar.

I tried everything to my ability, the problem started with V2.3.4 on 8.04LTS, now updated to 10.04LTS & 2.4.3, tear the Z-touch off hal apart & even unplug the par-port but the issue persist...

##Other info I use Atom board with 2G Ram on board & a 8Gig pendrive as hard drive...

Any help is highly appreciated.

Regards

Hi

As this wiki

linuxcnc.org/docs/2.4/html/gcode_coordin...html#sec:G92-Offsets

explains,

They can give rise to big errors and confusion, especially on machines without consistent mechanical homing or where no cancellation G92.1 command was used before quitting

( In the latter basically the increment is applied to the values pre-existing in the var file and results in excessive offsets which were unintended and could be the cause of your "exceed joint limit" error )

regards

I eventually isolated the problem to the use of G92. The X Y & Z coordinates will have a mind of its own & disregard what I type in the MDI command bar.

I tried everything to my ability, the problem started with V2.3.4 on 8.04LTS, now updated to 10.04LTS & 2.4.3,

Can you explain how you are using G92, and are you saying that there was not a problem with it before 2.3.4?

Rick G

Thanks for the response.

Rick,
1) I do have the same issue with 2.3.4
2) I use G92 for Z-axisZero touch-off 99% of the time..

Arceye,
Thanks for the link, but I just don't understand how its affecting...

Do you issue a G92.1 after using G92?

[url] linuxcnc.org/docview/2.5/html/gcode/gcod...id_sec_g92_1_g92_2_a [/url]

I use G92 to set the Z of my plasma torch with no issues.

Can you attach your G code file to a message?

John

Hi John,

The same problem persisted in any situation when ever I click on the Z-zeto touch-off the second time when I open up EMC2. & its not G-code file related.

:woohoo: I think I'd cracked the problem after digging deep into the links BigJohnT & Arceye posted earlier.

Before this, I never knew G92.1 & G92 existed :blush:
Always sometime new to learn

Its a mystery that this started only about 10 days ago after 2 years of operating with G92 without G92.1....

My solution
Issue a G92.1 command before every G92 command, this will reset the axis value that you worked on earlier. Than G92 what ever value to which ever axis I fancy. Not as convenient as before but at least I get it back to normal.

Maybe there is a better way, I'm all ears.


Thousand thank!


#PS, adding MDI-COMMAND G92.1 at the begining of the Auto Z-touch-off code line doesn't help.