Machine coordinate zero point in 5 Axis XYZAC

Hi,

I don´t understand the setup of the coordinates of a 5 axis XYZAC machine.
Where does an XYZAC configuration have its machine zero point?

According to the picture from linuxcnc, it is on the table an the offsets Dy and Dz can be set. In this case "G53 G0 Z0", defined as safety retraction  would be fatal and the tool would run directly into the table. In my understading, to still run "G53 G0 Z0" the machine zero would need to be higher, as scetched in the picture below. In that case, how do i tell linuxcnc where its center of rotations lies?



Thanks in advance.
edit: I know it displays a XYZAB machine, but that should´t be an issue to my question.

Yes, the machine origin is on the face of the 5 axis trunnion. It has to be there for the math to work.

Where do you input Dz and Dx values?

offsets can be found here:

linuxcnc.org/docs/html/motion/5-axis-kinematics.html
under "7. Custom Kinematics Components"

@Roiki: If that´s the case, then how do I set up my G53 G0 Z? in the postprocessor? I´m using the 5 Axis LinuxCNC PP.