Hi all, I recently setup an hobby GRBL 1.1 laser engraver with lightburn. When I start the machine, I home it manually(no limit switch) and send commands to zero the absolute coordinates. The machine works ok, however when I stop a job with the STOP button in the Lightburn laser panel, the coordinates that Ligthburn reads after that are completely messed up and often (maybe always) out of soft limits. I also get this error in console:
Job halted
Stream completed in 0:03
ALARM:3
Reset while in motion. Grbl cannot guarantee position. Lost steps are likely. Re-homing is highly recommended.
Any idea why this is happening? I would like to preserve the correct laser coordinates even after stopping a job.
Telling GRBL to STOP causes it to turn off the motors without regard to the usual deceleration limits, which is what “Reset while in motion. Grbl cannot guarantee position” means.
If you use PAUSE, then GRBL will obey the deceleration limits and maintain control over the position. After that, you can hit STOP with impunity, because nothing is moving.
Thank you ednisley. It think there is something more messed up here. I understand the error message, however the coordinates are really out of logic. I am now finding myself after a stop with X=3286 Y=1634 mm whilst the machine only has an area of 500x600 approximately.
Also the Pause method does not work either: I do not get the error message but the coordinates still result being completely out of whack after I stop.
There is no logic: the controller does not guarantee anything about the position after a STOP that causes an immediate halt, so you cannot proceed without (re)homing the machine and starting over.
Color me only mildly surprised, as nobody knows what they’ve done to the GRBL code in the machine.
Although you may want to preserve the coordinates, that option does not seem to be on the table. None of this has anything to do with LightBurn, because the controller firmware is in charge.
IMO the bottom line is “If it hurts when you do that, don’t do that.”
Stop basically means you ended the job, and you are starting all over.
I have paused a job, but only between layers and resumed without problems.
Once you hit start you are committed and only stop because things went sideways.
Maybe I will try to send some other type of pause/stop command through the console. Since my machine cannot mount limit switches and structure of the machine is not too stable, the homing operation is not really precise, this means that my following cuts/engravings can end up being not completely aligned, and also requires a bit more time. So I’d need to find a solution for this.
