Lightburn Connection Broke on an 8h Job - how to resume?

Hey guys,

Im quiet new to Laser Engraving and have a very important question.

I was engraving a PNG, it worked fine for about 4 Hours (~51÷) until My wife accidentally pull of the usb cable.

The connection got loss and the laser went back to its home position.

I saved the GCode immediately and tried Start GCode but the laser went back to the 0÷ Position and was going to laser everything again what has already been lasered.

Now my question, how can I continue where the laser stopped and got the connection loss?

I hope you guys can help me out shortly, because its a present for tomorrow. :sweat_smile:

Open the preview window (Alt+P or the button that looks like a TV monitor in the top toolbar).

Drag the slider to where the job stopped, then click ‘Start here’ on the bottom of the preview window. That will run the job from that point forward.

Hey mate, thank you for fast response. I don’t have the button: Start from here, only “Save Image” and “Ok”

Then you’d need to update your version of LightBurn to get it.

If the project is just an image, you can also change the Scan Angle in the image layer to 180 degrees, and that will burn top-down instead of bottom-up. Then you just have to stop it when it meets the part that’s already burned.

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Okay, so for now, I save my project als .lb*-File, Update Lightburn, open my saved project and do the steps you told me above?

The 180 degree fix wouldn’t require updating. If you want to use the ‘start here’ button, then yes, save the project, update, load it again and follow the steps I outlined.

Ok that worked. Now I’ve got another problem.

I didn’t move or touch the object I’m lasering nor the laser itself, it is on fixed position, as the object aswell, I didn’t even move the img inside of lightburn, but the laser is lasering a few mm beside the original position. How can I fix that? And why is this happening?!

Did you re-home the machine? You would need to, in case it lost position when the job aborted.

Could you tell me what you exactly mean? Re-Home like just press the home button?

Yes - homing the machine will make it bump off the limit switches and reset it’s position reference.

I did that, still the same problem :confused: any suggestions?

Have a look at this Image, totally wrong position.

It also looks really out of focus. Did you change the height? If the beam isn’t perfectly vertical, that could shift the alignment too.

Tbh mate, i didn’t change anything. Its really weird to me aswell.

You’ve got another idea?

Trust me I’ve changed nothing, I’m programmer so I’m used to computers and software :rofl::sweat_smile:

I can’t say why it moved. If you’re using “User Origin” or “Absolute Coords” mode, and your machine has accurate limit switches, the alignment should be exact.

What am I supposed to use? User origin or absolute coords? Tbh, even after reading the doc I still don’t know when or for what I have to use the different modes.

Could you please explain it user friendly and for those who doesn’t got that much experience on laser engraving?

Absolute Coords means that where the shapes are drawn in LightBurn is where they go on the laser, period.

User Origin means that you jog the laser to a spot then click the ‘Set Origin’ button, and that position is now the “green square” in LightBurn in your job. So if the job is below and to the left of that green square, it will run below and to the left of wherever you set the user origin. Does that help?

The key here is that both of those use a stored, fixed reference value. Using “Current Position” means that the job runs similar to ‘User Origin’, but runs from wherever the laser head is when you click ‘Start’, not from any saved reference point.

If I get you correctly, with the option user origin I’m able to move the position of the image I want to engrave to a different position on the engraving object referred to the position shown in lightburn? So the actual position of the img inside of lightburn doesnt matter, it will engrave the image to my user origin position, is that correct?

Yes, that’s correct. In ‘User Origin’ or ‘Current Position’ modes, the green square shows the position of the laser head relative to the design when you start the job. In ‘User Origin’ mode, the system jogs to the stored origin point first, then runs the job from that stored point. In ‘Current Position’ mode, it just starts from wherever the laser is currently placed. In both of those modes, the position of the artwork on the grid in LightBurn doesn’t matter.

you can also change the Scan Angle in the image layer to 180 degrees, and that will burn top-down instead of bottom-up. Then you just have to stop it when it meets the part that’s already burned

Now that’s a trick I didn’t know. Awesome!