Hello,
is it possible to somehow save the GCode completely in G90?
My machine (homemade) runs with Estlcam including a clamp adapter.
However, this control cannot process G91 commands.
So I could only cut with this and not engrave.
But I actually wanted to engrave too.
Can you give me any tips on how I can save the G-Code in absolute values?
Thank you
Greetings Jan
This is not the Ortur LM2, right? I may be speaking out of turn here, but I think incremental moves (G91) is integral with the design of Lightburn.
I find it difficult to accept CNC software cannot process incremental moves, but I see that it is so with Esticam. Have you looked at Carbide Create for your CAD/CAM package?
Why not just use Lightburn to feed the CNC controller? You can use Lightburn on more than one machine. Are you using a CNC controller board in your homebrew that is running GRBL?
Hello,
no, it is not the Ortur LM2 (actually it is a self-made CNC machine that I want to equip with a laser module so that I can also cut and engrave larger things).
Lightburn cannot control the machine.
GRBL doesn’t really work with the terminal adapter either.
For this reason I wanted to export the GCode from Lightburn and then process it normally on the machine.
Cutting or normal lines work.
But everything that is output as an engraving (image/filled font) cannot be processed by the control because these are all G91 coordinates.
This means that the machine only ever moves back and forth within a millimeter range.
So there’s nowhere to switch to G90 in Lightburn?
Why Carbide Create?
Thank & Greetings
No, even if you use Absolute Coordinates in the Laser window, it will out G90, then later show G91 codes.
Carbide Create was just a suggestion. It may output everything as G90, but I am not sure. I just recently downloaded it.
Incremental motion is much easier to process than absolute. It is just go here, go there with no worry about where you really are.
Not sure what this means. You can feed commands to a GRBL controller with puTTY, Lightburn, or any other terminal program.
I don’t think the Estlcam controller (board in the control cabinet) can process GRBL. That’s why I wanted to create the GCode with Lightburn. Well at least the cutting works.
I did not realize this. I Googled it and just saw CADCAM software. 8-bit GRBL controller boards are dirt cheap on Amazon.
How should I integrate an “8-bit GRBL controller board” into my machine. Everything is controlled by the EstlCam terminal adapter (board).
Hardware:
Thanks
That looks more like an industrial controller than a MakerSpace item. I expect it would require a ground-up revision. I guess you have to decide how bad you want G91 capability.
Maybe you can find a low cost CADCAM program that you could import the incremental Gcode program and convert it to absolute positioning. I really don’t have a good solution for you!
Are you talking about the positioning? Change “start from” in laser window from “current position” to “absolute position”. Then all commands are absolute coordinates, no increments.
Also in the G-Code when you save it?
Yes, looks like that. That’s also what I would have expected. But I don’t know if you machine can handle this then. 
I thought it would do a G90, then a few lines later do a G91. But this snippet of a test file using 1.4.03 confirms what Melvin said.
; LightBurn 1.4.03
; GRBL device profile, absolute coords
; Bounds: X102.03 Y174.32 to X173.69 Y289.28
G00 G17 G40 G21 G54
G90
M4
; Cut @ 1800 mm/min, 35% power
M8
G0 X120.488Y175.279
; Layer Cut
G1 X121.314Y175.034S350F1800
G1 X122.149Y174.825
G1 X122.991Y174.652
G1 X123.839Y174.514
G1 X124.692Y174.413
G1 X125.549Y174.349
G1 X126.409Y174.321
G1 X127.27
G1 X127.901Y174.359
Use of Absolute Coords does not guarantee exclusive use of G90. Certain conditions will call for G91. I’m not familiar with all the criteria but at least using a fill operation will show this.
Create a simple rectangle with fill using Absolute Coords. The resulting G-code should show a transition to G91 for the fill.
So I am not senile after all!!! I thought I saw this with my CNC mill, aka Laser, when messing with Zaxis moves.
Found it…
; LightBurn 1.4.00
; GRBL device profile, absolute coords
; Bounds: X12.58 Y21.38 to X185.42 Y44.63
G00 G17 G40 G21 G54
G90
M4
; Cut @ 1000.002 mm/min, 100% power
M8
G0 X26Y21.375
G91
G0 Z-18
G90
; Layer Cut
G1 X12.577Y44.625S1000F1000
G1 X39.423
G1 X26Y21.375
G0 X34.577Y21.375
Z-axis is its own little corner case. LightBurn allows for some configuration of Z-axis behavior in Edit->Device Settings. “Relative Z-moves only” will guarantee moves in G91. I’m not sure if disabling that necessarily guarantees absolute positioning but since Z-axis is somewhat special cased in LightBurn I could see that occurring.
That makes sense! Not that it matters for me, but I will do some more testing. Thanks to all for something else to learn.
Lightburn: The education that keeps on giving. 
Confirmed!!
; LightBurn 1.4.03
; GRBL device profile, absolute coords
; Bounds: X61.54 Y139.96 to X227.02 Y289.28
G00 G17 G40 G21 G54
G90
M4
; Cut @ 1800 mm/min, 35% power
M8
G0 X120.488Y175.279
; Layer Cut
G1 X121.314Y175.034S350F1800
G1 X122.149Y174.825
G1 X122.991Y174.652
G1 X123.839Y174.514
G1 X124.692Y174.413
G1 X125.549Y174.349
G1 X126.409Y174.321
G1 X127.27
G1 X127.901Y174.359
G1 X129.3Y174.502
G1 X130.681Y174.737
G1 X132.041Y175.063
G1 X133.374Y175.478
G1 X134.677Y175.98
G1 X135.946Y176.569
G1 X137.175Y177.242
G1 X138.36Y177.998
G1 X139.42Y178.764
;—(SNIP)—
G1 X109.252Y183.236
G1 X109.954Y182.404
G1 X110.686Y181.598
G1 X111.449Y180.82
G1 X112.428Y179.903
G1 X113.455Y179.046
G1 X114.529Y178.252
G1 X115.645Y177.522
G1 X116.803Y176.858
G1 X117.998Y176.262
G1 X119.227Y175.735
G1 X120.488Y175.279
; Scan @ 200 mm/min, 100% power
M8
G0 X120.188Y140.277
M3
; Layer Names Pass 1 of 2
G91
G0 X0.084
G1 X2.368F200S1000
G0 X0.083
G0 Y0.08
G0 X-0.083
G1 X-2.368
G0 X-0.084
G0 Y0.08
G0 X0.084
G1 X2.368
Looks like we are back to this question…
LightBurn always switches to relative moves when doing fills, because they tend to generate more compact gcode. There is currently no way to tell LightBurn to emit only absolute moves.
Hello,
Ok, thank you very much.
For the Lightburn developers, it shouldn’t actually be a problem to add an option so that you can choose how the GCode should be output.
In my opinion, it would be a very useful feature for users who work with Estlcam, for example.
Thank you, greetings Jan
