Hey Tony,
the g-code command sequence
G53 G0 X4 Y3
moves rapidly to X=4 and Y=3 in machine coordinates (no matter what coordinate system is in effect). If you want to be at a safe height prior to it you would add a preceding line that says
G53 G0 Z0
which will lift Z to the upmost position.
If you want to make the X=4 Y=3 (to which you moved rapidly above) your new workpiece zero, finally you do:
G92 X0 Y0
From this moment on, your X=4, Y=3 is the new X=0, Y=0.
Alternatively, if you don’t want to move to the new position but only set it your new workpiece zero, if you’re still at home position (or use G28 Z0 to go home with first lifting Z), you can simply enter:
G92 X-4 Y-3
From this moment on, your X=4, Y=3 is the new X=0, Y=0.
Explanation
G0 Move rapidly (if tool=laser, not firing)
G1 Linear Move at given feedrate (if tool=laser, firing)
F Set Feed rate
G90 Set Absolute Distance Mode – distances are meant to be in the active coordinate system
G91 Set Incremental Distance Mode – distances are meant to be relative to the coordinate you are at the moment
G53 Move in machine coordinates – no matter what coordinate system is in effect, it won’t change the latter.
IMPORTANT NOTE: Unlike the coordinate system commands G54–G59.3, G53 is not modal, it must be programmed on each line. G0 or G1 does not have to be programmed on the same line if one is currently active.
G92 Coordinate System Offset axes – makes the current point have the coordinates you want (without motion)