Registering on an existing burn to reburn

I did a less-than-desirable thing: I completed a burn of an image…after moving the piece, I’d decided that I’d like it to be darker and would like to reburn it. I’m fairly certain of the registration of the piece, but would like to be able to confirm it before starting a reburn.

I used center as my starting position - and chose the burn from current location option. I still have the center spot marked on the piece and feel good that I can get it close enough. Due to the nature of the image, small inaccuracies will be unnoticeable, however, if the piece is not perfectly plumb to where it was the first time, those small inaccuracies will get worse, the further the burn gets from center. So, I’d like to confirm the registration of the piece at its extremities before starting the burn.

Is there a way to locate a spot on the LightBurn diagram and move the laser to that specific location on the piece? I see a “Position Laser” option, but I’m not sure how to use it. I feel confident that, if I can spot a few key locations on the image, that I will have the piece in a suitable alignment and be able to reburn, close enough for that image.

Thanks

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You can, as you suggest, use the ‘Position Laser’ tool to click an exact location on-screen, and the laser head will move to that exact physical location of your laser.

image

With you laser properly tuned and connected, simply select this tool in LightBurn, then with the mouse, click somewhere, anywhere on the on-screen grid displayed and you should see the laser head start to move toward that physical location of your laser. That’s all there is to this tool. Speed of movement is based on the settings in the ‘Move’ window.

And if you think this is something you may have to deal with regularly, take note of the section I have highlighted in gold. You can read where your laser thinks it is currently, move to an exact location, save and recall an exact positions allowing you to repeat a process with known, saved locations.

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How do I tell LightBurn that the laser is currently at the start point of my diagram? If I can do that, then if I pick a point relative to that and press Position Laser, it will go to the right place. Do I need to “Home” the machine first - or the equivalent? I’ve had trouble with homing before (as in, the head tried to leave the surface of the machine) - so I’ve been always setting the start point at center, then moving the laser to the center point and starting the job from current position.

And, by the way, my version of LightBurn does NOT look like yours! I don’t think I have a “Focus Z” or a continuous jog switch. What version is that?

Answering my own question, I think: Does “Set Origin” tell LightBurn that the current position is the Origin of the diagram (in the case I’m stating, it would be the center of my design)?

If so, then my procedure will be:

  • Set the laser to the center mark of my piece
  • Press “Set Origin”
  • Then click the teardrop icon
  • Click on a spot on my design
  • Click “Fire”
  • Check that the location is where I expect it to be
  • Rinse and repeat for other locations

Sound right?

You will find that LightBurn Staff will post using the latest public release for consistency. You should keep in mind we offer a Mac version, 2 Windows versions, and another for Linux so this can present differently.

Most importantly, LightBurn supports an ever-growing list of laser systems with different feature sets. The LightBurn User Interface (UI) is dynamically adjusted, based on the currently selected ‘Device Profile’ so only relevant options are presented. At the time I screen-capped the images above I had ‘Ruida’ as my selected profile. You are using something very different and that is what you are seeing.

You don’t need to…we have some documentation that you can reference and it’s straight from the source :wink: : https://lightburnsoftware.github.io/NewDocs/CoordinatesOrigin.html

I upgrade immediately. I’ve worked in software. The only thing I don’t automatically install is an x.0 release!

Since I’m using relative addressing, I’m guessing I do need to tell LightBurn where my origin is before using the Position Laser tool direct the laser to a point on the diagram. I’ll just try it and hit the panic shut off if it starts to wander to the edges of my machine.

Home your system to 0,0 and go from there. I might be completely missing what you are wanting to do here, but if you home your properly configured setup, LightBurn should report that you are at 0,0. Is this not happening for you?

I’m not using absolute coordinates, I’m using relative coordinates. I keep my designs origin’d at their centers. I then position the laser on the center mark of my substrate and “Start from Current Position”. I’m not “homing” my machine at all.

The question here is whether the “Position Laser” tool uses absolute coordinates to position the laser, or does it reference my origin? I can trial-and-error this tomorrow, unless you know the answer off hand.

This does not work.

I’m guessing that the Position Laser tool uses the absolute coordinates of the system, rather than the origin of the design that’s in the system at the time.

I brought in my file, positioned the laser over the origin, Pressed Set Origin, selected the Position Laser tool and clicked on the origin again (expecting it to not move at all, since it was already on the origin). The laser began to move left and left the work surface of my CNC - I hit the panic button to stop it from trying to exceed the left side gantry.

So my GUESS is that Position Laser is using absolute coordinates and therefore the CNC needs to be homed before you use it. Since I’ve always used relative coordinates, I’ve never had to home the CNC to use the laser. I always home it before using the CNC for routing (using Carbide Motion)…but never had to do it with LightBurn.

Can someone point me towards the instructions for homing the CNC in LightBurn? I have a Shapeoko XXL with proximity sensors.

By the way: Wouldn’t it make more sense to have the Position Laser tool respect the “Start From” setting?

In other words, if Start From = Absolute, then the PL tool would use the absolute location of the click…but if you set either “Current Position” or “User Origin”, it would use that as the reference for where the gantry should bring the laser. I don’t understand why it wouldn’t.

@LightBurn: Would you be willing to weigh in here?

The ‘Position Laser’ tool is moving the laser to the point in the design space that you click, and yes, it uses absolute coordinates - it has to. If you used ‘Current Position’, the moment you moved the laser, the current position would be different, and subsequent clicks wouldn’t work.

If your laser doesn’t home, that’s an issue with the configuration of the machine, the wiring, etc - all LightBurn does is send the homing command and the controller takes it from there. Homing is covered well in the GRBL docs:

here: https://github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#22---homing-cycle-boolean
and here: https://github.com/gnea/grbl/wiki/Set-up-the-Homing-Cycle

@LightBurn I agree on Current Position…but let me argue that “User Origin” WOULD be a valid option - and one that would be VERY helpful for the problem I’m facing. For a user who uses relative coordinates all the time when in LightBurn - and who has NO idea what the absolute coordinate is for any given design (I’m always just aligning center of the workpiece and letting it rip from there), it would be greatly helpful to be able to set the user origin - which LightBurn then knows as a fixed point and then position the laser relative to that.

Closing the loop:

  1. I homed the machine after clicking on “Use Laser”
  2. Loaded my design
  3. Used Position Laser to position the head on the origin of my design
  4. Moved the workpiece under the laser so that the origins aligned
  5. Used Position Laser to spot a few more points in the design, and adjusted my workpiece’s position
  6. Relocated the origin
  7. Ran the burn

AND IT WORKED PERFECTLY!

I’d still like to see Position Laser be able to run from User Origin - which would eliminate steps 1,3, and 4…but hey, it worked.

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