HEIDENHAIN iTNC 530 (340 49x-06) Pilot - Manual (Page 170)

170
Definin
g
Mac
hin
ing P
o
sitions
Changing the starting height
U Top surface coordinate : Coordinate of the top surface of
the workpiece
If you do not define a starting height in the definition of the
machining positions, smarT.NC always sets the coordinate of
the workpiece surface to 0.
If you change the starting height, then the new starting
height is valid for all subsequently programmed machining
positions.
If you select the symbol for the top surface coordinate in the
tree view, then all machining positions for which this starting
height is valid turn green in the preview graphic.