Skip to content

Troubleshooting - GRBL

GRBL has a number of different internal error codes that you might see when using LightBurn. These are the most common:


If you are getting the 'Busy' bar in LightBurn, but the machine does not move, make sure you are actually connected to the controller. You may need to select a communication port (see connecting to the laser) and if you can't choose a port, it's possible that you need to install the drivers or software that came with your machine before your computer can talk to it (see connection issues).

Machine is busy or paused

If you are seeing this error, most likely you have not actually connected to the machine yet. Make sure you have installed any drivers required by your hardware, and make sure you have chosen a communication port to connect to. When connected, the console should contain messages sent from the controller. If you are not connected, look in the laser window where the mouse pointer is shown below:

If you click where it says "(Choose)" and the list does not contain any names, or you have tried them all, you might need a driver for your controller to connect to the computer. A common one for Chinese diode engravers is this one:


You are trying to send the machine outside of its known working area, and GRBL has prevented this in order to prevent damage to the machine. This can happen for several reasons:

  • You are actually trying to run a job that exceeds the size of the machine work area.
  • You are trying to run a job in 'Current Position' or 'User Origin' mode and haven't properly set the Job Origin or User Origin settings. Read here: Coordinates and Job Origin
  • You have your machine misconfigured, possibly trying to run a negative workspace machine without a workspace offset: Common GRBL Setups


This means that LightBurn sent the command to the controller to home it, but the controller does not have homing enabled or configured. The most likely reason for this is that the machine does not have homing switches, and you turned on 'Auto-home on startup' in the device settings.