Z-Offset for Scribe

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01 Aug 2022 07:19 #248774 by Daddio
Z-Offset for Scribe was created by Daddio
Hello all,
I am running QtPlasmaC on 2.9.0 with sheetcam.
I added a pneumatic scribe that is mounted to the Z carriage that when actuated is driven down on a slide - pretty typical.  Everything seems to be working except my slide can't reach the material.  How do I add a Z offset for an engraving/scribing operation?  
This is a problem when scribing is the first operation because Z is high up at Z home-offset.  Whereas if a cut is the first operation, then the next engraving op is actuated from Safe Height rather than Z home-offset.  
I tried adding a Z offset at   T1 P1 X0 Y0 Zx ; scribe   in the tool.tbl to the scribe tool, but it didn't do anything.  It would be awesome to have a field to set the scribe height similar to the probe height. 
Thanks!

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01 Aug 2022 11:55 #248784 by LesNewell
Replied by LesNewell on topic Z-Offset for Scribe
The tool table seems an obvious place for this. I'm not sure why it is not working. Maybe take a look at your logs to see if there is something in the tool table LinuxCNC does not like.
Try manually editing your g-code. Look for G43 H0. Change the H parameter to the tool number. For instance if your scriber is tool number 1 you'd have something like this:

N01230 T1 M6
N01240 G43 H1


If that does not work I should be able to modify the post to add an offset.

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01 Aug 2022 12:17 #248786 by andypugh
Replied by andypugh on topic Z-Offset for Scribe

I tried adding a Z offset at   T1 P1 X0 Y0 Zx ; scribe   in the tool.tbl to the scribe tool, but it didn't do anything. 


You need a G43 to apply the tool offset.

I suspect that is all that is missing.

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01 Aug 2022 14:54 #248791 by Daddio
Replied by Daddio on topic Z-Offset for Scribe
Hi Les,
I changed:
T1 M6
G43 H0 --> G43 H1
but got the same results, it doesn't grab the z offset.

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01 Aug 2022 17:11 - 01 Aug 2022 22:54 #248799 by snowgoer540
Replied by snowgoer540 on topic Z-Offset for Scribe
The intent of the behavior of the scribe is that when it is "armed", the pneumatic cylinder would make the scribe touch the material.  I suppose if moving the scribe's slide closer to the material is not an option, then you could try  Keep Z Motion  for the scribe portion of your cut file.  In this case you might consider providing the coordinates via G53 so that resetting the DRO wont affect where the Z axis is positioned.  

An easy way to set this would be to use a variable:

EDIT: see below for correct code


Where 1.001 is the distance measured from the top limit switch down.  
Last edit: 01 Aug 2022 22:54 by snowgoer540.

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01 Aug 2022 17:37 #248800 by Daddio
Replied by Daddio on topic Z-Offset for Scribe
snowgoer540,
That throws a "bad number format (conversion failed) parsing" error..

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01 Aug 2022 17:58 #248801 by snowgoer540
Replied by snowgoer540 on topic Z-Offset for Scribe
I'll try to take a look after work.

does it fail on
#<keep-z-motion> = 1

or the G53 line I pasted above?

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01 Aug 2022 18:11 - 01 Aug 2022 22:55 #248802 by snowgoer540
Replied by snowgoer540 on topic Z-Offset for Scribe
I think this may be wrong (i copy pasted from the qtplasmac manual, but it doesnt match the gcode filter):


EDIT: see below for correct code


You could just use the actual number.  G53 G0 Z-3.500

obviously change -3.500 to suit your needs.
Last edit: 01 Aug 2022 22:55 by snowgoer540.

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01 Aug 2022 18:59 #248804 by Daddio
Replied by Daddio on topic Z-Offset for Scribe
Yeah, something is up with the G53 G0 Z[{AXIS_Z MAX_LIMIT} - 1.001] line.

#<keep-z-motion> = 1 works no problem, same with the G53 G0 Z-3.500 at first test.

I'm basically adding it in as a code snip in sheetcam.
The following user(s) said Thank You: snowgoer540

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01 Aug 2022 22:49 - 02 Aug 2022 20:54 #248812 by snowgoer540
Replied by snowgoer540 on topic Z-Offset for Scribe
This should work:


g53g0z[#<_ini[axis_z]max_limit>-3.5]



3.5 would be whatever you need it to be of course.

Edit:  I should note that I grabbed the original code I posted from the button code section of the QtPlasmaC manual without thinking.  So, that would work for button code, but not for G-Code.  Sorry about that :)
Last edit: 02 Aug 2022 20:54 by snowgoer540.

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