G92 messing up the coordinate

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26 Feb 2012 07:18 - 26 Feb 2012 07:25 #18089 by KenC
To put things real simple. I use G92 to assign new coordinate value. Mostly on Z axis.
It will work nicely for the 1st time when I open EMC. & I can run a .ngc happily with it.
& when I wish to assign a new coordinate with G92, the warning bar at the bottom right of AXIS screen will flash "exceed joint's negative limit". without fail.
When I use G92.1, it will reset the DRO coordinate values but still flashes the "exceed joint's limit" warning.
So what I do to continue with work is G0 0,0 & close EMC. Re-open EMC & home all the axis all over again.

Again, I do my homing manually as I don't have limit switches installed.

I tried G10 L20, but I get warning asying "out of range"...

Regards

KEn
Last edit: 26 Feb 2012 07:25 by KenC.

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26 Feb 2012 09:34 - 26 Feb 2012 09:45 #18092 by Rick G
Be sure to use P with G10

Such as G10 L20 P1 X0 Y0

Have you looked at your tool table?

Have you made sure all offsets are off such as G49?

linuxcnc.org/docs/html/gcode_main.html#sub:G43,-G49:-Tool

Rick G
Last edit: 26 Feb 2012 09:45 by Rick G.

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26 Feb 2012 11:27 #18095 by BigJohnT
I use G92 all the time on my plasma table so I know it does not mess up my coordinate system. Can you attach a bit of code that will reproduce the problem so we can help you?

John

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26 Feb 2012 12:08 - 26 Feb 2012 12:17 #18097 by Rick G
As John said...

I use G92 all the time on my plasma table so I know it does not mess up my coordinate system


So do I on my router, mill and lathe without a problem.

You might want to look here..
linuxcnc.org/docs/html/common_User_Concepts.html#r1_5_3

Rick G
Last edit: 26 Feb 2012 12:17 by Rick G.

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27 Feb 2012 04:01 - 27 Feb 2012 04:07 #18111 by KenC
Hi John,
I write single command on the MDI screen. It will do its black magic everytime.

G92 Zxx.xx (xx.xx being any number, + or -ve)

That is all I need to do to screw everything up.

Hi Rick,
Thank for the pointer, will dig deep into the links you attached.

Thousand thanks.

Ken
Last edit: 27 Feb 2012 04:07 by KenC.

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27 Feb 2012 12:38 #18126 by BigJohnT
Gee, can you be a bit more precise than "black magic" G92 Z anything works as expected for me and everyone else.

John

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27 Feb 2012 12:56 - 27 Feb 2012 13:05 #18127 by KenC
John,
I have no idea what is the word to describe it...

I get “exceed join'ts limit" faithfully whenever I issue a second G92 command every time & if I ignore it & continue working, the machine will go to coordinates which are totally outside of all the soft limits.

This happens the same with V2.3.4 on 8,04 & the current 2.4.7

I have no intention to act like I'm cute or funny... but honestly, I have no other words to describe the mess made after I issue a G92 single command from the MDI command bar... everything is a mess & as these software "vocab" is voodoo to me...


Rick, I am not re-setting the machine co-ordinates, I still need the coordinated to remain so that the machine won't rush out of the soft limits. SO that G43, G49, G53 are not the things I want... I just want to re assign the work co-ordinate & not the machine cordinates.

Regards

Ken
Last edit: 27 Feb 2012 13:05 by KenC.

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27 Feb 2012 13:07 - 27 Feb 2012 13:08 #18128 by BigJohnT
Ok, Do you have a G54 offset in effect for the Z axis? In 2.4.x go to Machine > Zero Coordinate System and zero out the P1 G54 (which I assume your using).

Also, do you have a tool loaded with Tx M6 G43?

John
Last edit: 27 Feb 2012 13:08 by BigJohnT.

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27 Feb 2012 13:12 #18129 by KenC
Hi John,
I never touched that section of the screen I left it as default.
Anyway, I just did selected P1 G54 as you describe.

"Also, do you have a tool loaded with Tx M6 G43?"
I have no idea what this is.

Regards

Ken

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27 Feb 2012 13:21 #18130 by BigJohnT
When you Home your axes does the DRO show 0.0000 for all axes?

Does the bottom line say ON No tool Position: Relative Actual?

John

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