HEIDENHAIN TNC 426B (280 472) ISO programming - Manual (Page 51)

35 HEIDENHAIN TNC 410, TNC 426, TNC 430
X
Y
30
20
50 30 10
10
X
Y
20
10
10
20
10
10
Absolute and relative workpiece positions
Absolute workpiece positions
Absolute coordinates are position coordinates that are referenced
to the datum of the coordinate system (origin). Each position on the
workpiece is uniquely defined by its absolute coordinates.
Example 1: Holes dimensioned in absolute coordinates
Hole
Hole Hole
X=10 mm X=30 mm X=50 mm
Y=10 mm Y=20 mm Y=30 mm
Relative workpiece positions
Relative coordinates are referenced to the last programmed
nominal position of the tool, which serves as the relative (imaginary)
datum. When you write a part program in incremental coordinates,
you thus program the tool to move by the distance between the
previous and the subsequent nominal positions. Incremental
coordinates are therefore also referred to as chain dimensions.
To program a position in incremental coordinates, enter the
function G91 before the axis.
Example 2: Holes dimensioned with relative coordinates
Absolute coordinates of hole :
X= 10 mm
Y= 10 mm
Hole referenced to hole Hole referenced to hole
G91 X= 20 mm G91 X= 20 mm
G91 Y= 10 mm G91 Y= 10 mm
Absolute and incremental polar coordinates
Absolute polar coordinates always refer to the pole and the
reference axis.
Incremental polar coordinates always refer to the last programmed
nominal position of the tool.
X
Y
0°
30
10
CC
R
H
G91+H
R
R
G91+H
G91+R
4.1 Fundamentals of NC
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