Origin after Homing Confusion

Hi everyone,

Just purchased Lightburn to power my home built (and designed) laser cutter based on GRBL. Very impressed by the software BTW.

The software is great and everything pretty much works out of the box. However I am having one issue that I can’t seem to resolve myself. This is likely me doing something wrong rather than an issue with the software but I was hoping for some advice and guidance please.

The problem is this:

(I have a test file that simply draws a rectangle close to the hard X and Y limits of the cutter)

Scenario 1. This scenario works.

I HOME the cutter (in LightBurn). Then I CLOSE Lightburn and open it again and load my file. If I hit the “Get Position” on the move tab it says X=0 , Y=0. I then start the job and it works fine.

Scenario 2: this doesn’t work.

I launch Lightburn and load my test file. If I hit the “Get Position” on the move tab it says X=0 , Y=0, Just like the first scenario. I then hit the Home Button (in Lightburn) and when I hit “Get Position” the co-ordinates come back as X= -630 and Y=-390 (these are the dimensions of my table set in GRBL if you ignore the -ve). If I try to run the code at this point the cutter hits the hard limit switches and alarms (To be clear the homing bit works fine, it crashes the limits when I send the cut).

The difference between the 2 scenarios is that if I use Lightburn to HOME the the cutter immediately before sending the job it crashes the limits - presumably the system thinks it needs to get to (0,0) before starting and as it thinks both axis are well into the negative numbers it crashes the limits before even attempting the cut.

Hope this makes sense.

Any help greatly appreciated


OK, I’ve tinkered around a bit more.

The negative numbers are generated by GRBL. doing a “?” at the console after a home reports (-630, -390).

Googled a bit and realised that GRBL defaults its origin to the top right of the plate. My workspace origin is bottom left.

My system homes to the bottom left. So it kind of makes sense that if (0,0) is top right and the home position is bottom left then the 2 negative co-ordinates are correct.

Although I can see why this may be happening I’m still confused as to how to handle this in LightBurn. As it stands it will always crash the limit switches if a cut anything with +ve co-ordinates.

It’s almost like I need to put an offset of (-630, -390) on everything when it gets sent to print. I’m surethats not the solution and I’m missing something fundamental here

This may well help:

Sorry that wasn’t the link I wanted.
Hit Docs (top of page) and scroll down to ‘Common GRBL setups’. That should explain how to configure the offset

Woohoo! yes!

I think that’s sorted it for me.

Wish I’d seen that doc before, Thanks David.

For info, in case anyone else has the same issue…

I have limit switches at both ends of each X and Y axis. I had set the direction Mask in GRBL to home at the bottom left (seemed logical to me at the time). Now that David pointed me at the above doc I have gone back to homing in the Top Right (which I think is the natural behaviour for GRBL). and then using the negative workspace system everything seems to be a lot more logical.

Thanks again


I assume the G10 offset will get forgotten by the controller when restarted?

So I should put the G10 code into the start gcode in LightBurn device settings so its set every time?

I only had to do it once, I assume that will be the case for you.

G10 offsets are remembered until cleared.

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