HEIDENHAIN ND 920 - Manual (Page 6)

6
Absolute workpiece positions
Each position on the workpiece is uniquely defined by its absolute
coordinates.
Example Absolute coordinates of position 1 :
X = 10 mm
Y =
5 mm
Z = 0 mm
If you are working according to a workpiece drawing with absolute
dimensions, you are moving the tool to the coordinates.
Y
X
Z
10
5
1
1
Y
X
Z
10
5
10
10
1
2
1
Relative workpiece positions
A position can also be defined relative to the previous nominal position.
The datum for the dimension is then located at the previous nominal
position. Such coordinates are termed incremental coordinates or
chain dimensions. Incremental coordinates are indicated by a preceding
I.
Example Relative coordinate of position referenced to
position
:
IX = 10 mm
IY = 10 mm
If you are working according to a workpiece drawing with incremental
dimensions, you are moving the tool by the dimensions.
Sign for incremental dimensioning
A relative dimension has a positive sign when the axis is moved in the
positive direction, and a negative sign when it is moved in the negative
direction.
Fundamentals
2