G2 and G3 Arcs not Responding to G92 Offsets
 
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Brad412
(@brad412)
Member
G2 and G3 Arcs not Responding to G92 Offsets

Apologies if this isn't the right place to discuss something like this, but I'm using PrusaSlicer G-code Viewer to help write and visualize some custom G-code, and saw some similar threads relating to technical questions so for now... this is where I'm posting it until otherwise directed. 

I have a custom G-code wrote, partially with CAM software actually (to have more control over movements), to print some fairly simple geometry. In short, I need to use G92 to simply "shift" my entire print over some given offset. See the example below noting that everything is in absolute:

 

G1 E0 X200 Y200 Z0 E10 ;Move to what will be the offset +200x +200y

G92 E0 X0 Y0 Z0 ;Call this location my new origin 

G1 X-34.159 Y120.231 F3600 E100 ;Move to the start location of the arc

G3 I34.159 J-120.231 F720 E785.332 ;Create an arc with no endpoint (a circle) at the current location 

 

To me... I don't see anything wrong with those lines of code. However PrusaSlicer G-code viewer is moving that arc an additional offset even though the G1 command before puts the head in the correct location. Looking at the remainder of the program, all of the G1 commands are as they should be, moving in some relation to this new origin offset (still in absolute). The arcs however are all shifted away from the origin as the first one is...

The I and J are relative are they not? How could an arc be made in a different location with no ties to its current location or a given endpoint? I have tried a multitude of things to avoid this problem, including adding a X and Y to the arc, calling G92 X_ Y_ at original origin without any translations, but the result is the same. Not sure what is going on here and any guidance or input would be appreciated. 

 

 

This topic was modified 1 month ago by Brad412
Posted : 12/04/2024 8:37 pm
Eef
 Eef
(@eef)
Estimable Member
RE: G2 and G3 Arcs not Responding to G92 Offsets

I do not know much about G-code (but a bit :-)) 
https://marlinfw.org/docs/gcode/G002-G003.html. is about G3
An example there: It can be generated either by G3 X2 Y7 I-4 J-3 or G3 X2 Y7 R5
So the G3 command starts with a X and Y part (setting the position? )
And I +J or R to create the arc. 
In your example I miss the X and Y 
G3 I34.159 J-120.231 F720 E785.332 
can it be that it should start with: 
G3 X34.159 Y-120.231 and some more information has to come here F720 E785.332 

Regards. Eef 

 

Posted : 12/04/2024 8:51 pm
Brad412
(@brad412)
Member
Topic starter answered:
RE: G2 and G3 Arcs not Responding to G92 Offsets

In your example I miss the X and Y 
G3 I34.159 J-120.231 F720 E785.332 
can it be that it should start with: 
G3 X34.159 Y-120.231 and some more information has to come here F720 E785.332 

Yes, that has been tried. Same results. I leave it in this condensed version so I ensure that my start and end are in the same place (a complete circle).

Posted : 13/04/2024 3:31 am
Neophyl
(@neophyl)
Illustrious Member
RE: G2 and G3 Arcs not Responding to G92 Offsets

The gcode viewer probably doesn’t handle it properly. Historically it has had issues with not supporting things as it only really supports the stuff PRUSA uses as “standard”. Remember that not every firmware or software that is compatible with a standard supports every part of it. There are many marlin functions that the printer firmware doesn’t support and so the gcode viewer is similarly limited. 
Try a different gcode visualisation tool. 

Posted : 13/04/2024 7:44 am
Eef
 Eef
(@eef)
Estimable Member
RE: G2 and G3 Arcs not Responding to G92 Offsets

 

Posted by: @brad412

In your example I miss the X and Y 
G3 I34.159 J-120.231 F720 E785.332 
can it be that it should start with: 
G3 X34.159 Y-120.231 and some more information has to come here F720 E785.332 

Yes, that has been tried. Same results. I leave it in this condensed version so I ensure that my start and end are in the same place (a complete circle).

Maybe we mis-understand. The G3 command needs information about the circle/arc. That is in the I, J and/or R part of the command. 
You use the X-Y coordinates as input for the I and J. 

Posted : 13/04/2024 8:10 am
_KaszpiR_
(@_kaszpir_)
Honorable Member
RE: G2 and G3 Arcs not Responding to G92 Offsets

One more thing, make sure to move comments above the gcode lines, not as inline comments at the end

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 13/04/2024 7:02 pm
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