HEIDENHAIN TNC 122 User Manual - Manual (Page 13)

1 Fundamentals of Positioning
TNC 122 13
Datums and positions
Y
X
Z
1
20
10
Z=15mm
X=20mm
Y=10mm
15
I
Z=–15mm
Y
X
Z
2
10
5 5
15
20
10
10
I X=10mm
I
Y=10mm
3
0
0
Absolute workpiece positions
Each position on the workpiece is uniquely identified by its abso-
lute coordinates.
Example: Absolute coordinates of the position :
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.
Fig. 1.5: Position definition through absolute
coordinates
Incremental workpiece positions
A position can also be referenced to the preceding nominal po-
sition. In this case the relative datum is always the last pro-
grammed position. Such coordinates are referred to as incre-
mental 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 referenced to
position
Absolute coordinates of position :
X =
10 mm
Y = 5 mm
Z = 20 mm
Incremental coordinates of position :
I X= 10 mm
I Y= 10 mm
I Z = –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. 1.6: Position definition through incremen-
tal coordinates
3
2
2
3
1