Inverting the x-axis
There was an issue with the default setting for the machine, where the x-axis was moving in the wrong direction meaning that we were getting parts that were a mirror image of what they should be!
This guide gives a full account of Grbl’s $x=val setting, in particular we needed several steps for this machine.
$4=1 to enable the inversion of the axes (allowing us to make the change) , then
$3=1 to invert the x-axis only, then
$4=0 to disable the inversion of the axes (disabling the ability to make changes).