G28, G30 (Return to Home)
Two home positions are defined (by variables #5161 to #5166 for G28 and variables #5181 to #5186 for G30). The variable's values are in terms of the absolute coordinate system but are in unspecified length units.
To return to the home position by way of the programmed position, program G28 X... Y... Z... A... (or use G30). All axis words are optional. The path is made by a traverse move from the current position to the programmed position, followed by a traverse move to the home position. If no axis words are programmed, the intermediate point is the current point, so only one move is made. The order of Z depends on its position, if the end position is higher than the current Z position Z will move first, otherwise Z will move last, this is to prevent collisions.
Addition for lathe: For a lathe the X axis is moved first, the assumption is that X moves away from the turning center.