Focus without "Fire" button

I’ve read the posts focused (pun intended) on using the “Fire” button to focus the laser. This works well if you focus by turning the lens. I prefer to fix the lens and adjust the Z-axis to get the smallest spot. However, the “Fire” button turns off as soon as I try a move. I understand the safety concerns for having Lightburn work this way. I’ve tried turning on the laser in the “Console”, but it turns off as soon as I try a Z-axis move. Maybe there’s another alternative I’ve not thought of??? Maybe someone has a solution? My work-around is to set the focus using UGS, determining the focus distance from the work surface to the bottom of the heat sink and then using that distance in all my Lightburn work. That’s OK, but I’d prefer to do everything in Lightburn.

As an aside, I’ve had some good luck in getting the smallest laser spot using one of these endoscopes:

I use a spring clamp to hold the camera end and place the clamp on a 2x4 to get a decent angle at the spot outside the laser beam. I put a little piece of the orange protection shield in front of the camera and turned its built-in lights off. The software that came with my camera allows for brightness and contrast controls (analogous to reducing the aperture of a SLR camera) to make the spot just barely visible (using M3 S1 command) with pretty sharp edges. I can move the Z-axis (using UGS) up and down to get to the place where the spot is the smallest. I measure from the surface to the base of the heatsink (Endurance laser) and take that number into LIghtburn. So far, it’s worked well.

All the move commands are issued as G1’s, but they turn the beam off (intentionally). You can just issue console commands if you want to - M3 will enable the beam in constant power mode, G1 Sxxx will set the beam to xxx power, and then G1 Zxxx will set the Z to xxx height. You should put an Fxxx rate on there too, at least for the first one.

G1 S50 F1000

and so on.

You could also try using the new Focus Test feature, which automates this. Tools > Focus Test.
Choose a start and end Z height, power, speed, and number of steps, and the software will cut a small pattern with varying Z positions (labeled). You can preview and frame from the pop-up to make sure it’s lined up. If you’re in Absolute Coords mode it will run in the center of the machine.

The thinnest line is your best focus height.


Excellent! The Gcode move commands do exactly what I need. Thanks! I will also try the built-in Focus Test feature.

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