- G28 and G30’s behavior has been updated from the old NIST g-code
standard to LinuxCNC’s. Previously when an intermediate motion was
programmed, the NIST standard would move all axes to the final G28/30
stored coordinates. LinuxCNC states it only moves the axes specified in
the command.
For example, suppose G28’s stored position is (x,y,z) = (1,2,3) for
simplicity, and we want to do an automated z-axis tool retraction and
then park at the x,y location. `G28 G91 Z5` will first move the Z axis
5mm(or inches) up, then move Z to position 3 in machine coordinates.
Next, the command `G28 G91 X0 Y0` would skip the intermediate move
since distance is zero, but then move only the x and y axes to machine
coordinates 1 and 2, respectively. The z-axis wouldn’t move in this
case, since it wasn’t specified.
This change is intended to make Grbl more LinuxCNC compatible while
making commands, like the shown tool retraction, much easier to
implement.
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