[mactec54]

G28 is not an "incremental" move and can be used in G90 absolute mode or in G91 incremental mode. Yes G91 is used most often, because it is easier, but G28 works in absolute mode as well.

G28 G91 X0 Y0 Z0 moves from where it is now in a straight line to the predefined position. Nothing incremental about that

G28 G91 X0 Y0 Z1 moves the Z up one unit and then it goes straight to the predefined position

I disagree that G53 is used more or is in any way better because to use it you have to set the machine coordinates that a G53 is going to. Use a different machine and the coordinates will likely need to be different Whereas with a G28, the coordinates are set at the machine and the program doesn't need to be modified. A CAM program can put a G28 G91 X0 Y0 Z1 but it can't put in a G53 unless it knows the coordinates it is sending to

To make that same move in G53 you need

G91 G0 Z1
G53 G0 X??? Y???? Z???? where the ??? are the coordinates of the G28 position.


G30 is just another predefined position and works just like G28.

Yes correct with the G28 it is normally used with a G91 I missed that bit

G30 does work like G28 G30 is return to 2nd 3rd &4th reference points a G28 does not do this and has very little use unless you have pallets or fixtures to move into different preset positions in the control other than normal Zero Positions

Here is some good information on these codes and how they work

https://www.cncci.com/resources/tips...28%20works.htm