HEIDENHAIN PT 880 - Manual (Page 15)

POSITIP 880 15
I – 1 F
u
ndamentals of P
o
sitioning
Absolute Workpiece Positions
Each position on the workpiece is uniquely identified by its absolute
coordinates. See Fig. I.6.
Example: Absolute coordinates of position 1 :
X = 20 mm
Y = 10 mm
Z = 15 mm
If you are drilling or milling a workpiece according to a workpiece
drawing with absolute coordinates, you are moving the tool to the
value of the coordinates.
Incremental Workpiece Positions
A position can also be referenced to the preceding nominal position.
In this case the relative datum is always the last nominal position.
Such coordinates are referred to as incremental coordinates
(increment = increase). They are also called incremental or chain
dimensions (since the positions are defined as a chain of dimensions).
Incremental coordinates are designated with the prefix I.
Example: Incremental coordinates of position 3 referenced to position
2 . See Fig. I.7
Absolute coordinates of position 2 :
X = 10 mm
Y = 5 mm
Z = 20 mm
Incremental coordinates of position 3 :
IX = 10 mm
IY = 10 mm
IZ = –15 mm
If you are drilling or milling a workpiece according to a drawing with
incremental coordinates, you are moving the tool by the value of the
coordinates.
Fig. I.6 Position 1 definition through absolute
coordinates
Fig. I.7 Positions 2 and 3 through incremental
coordinates