Siemens Sinumerik 840D Operating Turning page 57

Absolute and incremental dimensioning, mixed programming
2. 1 Absolute dimensioning
When writing CNC-Programs a fundamental differentiation must be made
between absolute and incremental coordinates.
Which of the two options the programmer chooses depends on the usage
of the program and the dimensioning on the drawing.
Absolute dimensioning: Code G90
All dimensions always refer to the active work piece zero point.
The absolute coordinates in a departure command describe the position,
to which the tool is to traverse.
Code G90 is usually activated as machine status when switching ON.
It is modally active for all axes simultaneously and can be reset to incre-
mental dimensioning with G91.
840D/828D SINUMERIK Operate
Coordinates,
an example for milling:
Workpiece zero point
G90 X
P1 20 35
50 60
P2
P3 70 20
Coordinates,
an example for turning:
(All X values are diameters,
DIAMON)
G90 X Z
25 -7.5
P1
P2 40 -15
40 -25
P3
P4 60 -35
Page 3
Section 2
Notes
Y
B503
B503