Preventing head crash with Focus Test

I crashed my brand new 4" head today when doing Focus Test. I set up reasonable limits for the low and high Z positions. However, LightBurn commanded the laser to raise the table above that limit after making the first line, apparently to print the label.
I searched online and found that the issue is known. I would greatly appreciate if the future version of LightBurn are made safer. Please consider following:

  • Default to relative Z moves only. I used the default “off” setting, but it’s a terrible, hardware damaging default!
  • Never move the table outside the specified range during the focus test, regardless of the “material thickness” that is set in a different window.

I’ll be extra careful in the future, but other users will thank you for not damaging their hardware.

Thunder Nova 51 130W, the latest LightBurn.

I have passed on your comments to the dev team, their response was that the default is currently set to be maximally compatible since some controllers do not support relative Z moves.

They are looking at adding code to check if relative moves are supported and to change the default accordingly, this should make future versions safer - so thankyou for your input.

Note - we do include warnings in our documentation on the potential hazards of these settings, and as a rule of thumb (for all controlled z axis, and even in future safer versions) I would suggest following the CNC best practice for testing something new, which is to run a test (“dry run”) with additional z clearance or with the nozzle moved up high or bed lower, so you can check the motion is as expected. Some people may even have their bed movement in reverse to what the tool expects, and a dry run will alert you of this, or any other potential for a crash.

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