Well ... think of it this way.
The G92 command writes directly to the machines position display. Whatever is in the G92 bloxk for X/Y/Z ... that's where the machine thinks it is.
For example ... take this ( fanuc ) code as a reference :
G00G91G28X0Y0 ... send X and Y to zero return or home position
G00G91X-1.00Y-2.00 ... make an INC move from there -1.00 in X and -2.00 in Y
G92X0Y0 ... this sets the machines ABS position to X0 Y0 ... the machine now considers this position absolute X0 Y0.
G00G90X-10.00Y-15.00 ... move to ABS position X-10. Y-15.0
At this point ... the tool would be -11.0 in X from zero return and -17.0 in Y
It would be -10.0 in X and -15.0 in Y from the point where it read the G92 line.
G92X0Y0 ... this would now set this current position to X0Y0
So you see you can move the ABS zero position around using the G92 command.
The drawback is it can get confusing following it and moving it.
With G54 thru G59 ... the distance from zero return or home to the desired X0Y0 locations can be stored in the G54-G59 offsets. When you make a command in the program like :
G00G90G54X1.00Y1.00
... the machine looks in the G54 offset to find the distance from zero return to the ABS part zero ... and then moves to the commanded XY coordinate using that value.
It is very easy to command G54X1.00Y1.00 or G55X1.00Y1.00 ... the values are all stored in the offsets.
Hope this helps a little down the road.
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