Siemens SIMATIC S5 Manual page 150

Machine Data, Modes and Traversing Programs
• G25: Approach target over the shortest path
G26: Approach target in a clockwise direction
G27: Approach target in a counter-clockwise direction
These functions can be executed for a rotary axis only, and are ignored for a
linear axis.
G25: Approach target over the shortest path
When the program is invoked, it defaults to G25. The IP computes the
direction of travel. If the distance is the same in both directions, the target is
approached from the preferred direction (clockwise).
The IP does not take backlash compensation into account when computing
the direction, thus making it possible that the longer path will be taken in a
small number of special situations. Figure 5-29 illustrates such a situation.
Backlash
270
180
Figure 5-29. Traversing of a Rotary Axis with Backlash
Prerequisites:
• The backlash compensation value was entered in the machine data
• G25 was programmed and the distance is the same in both directions
• The direction of travel in the last operation was counter-clockwise
5-78
0
270
90
180
Traversing movement by the
backlash. Actual value is still
0/360 degrees
0
270
90
180
Traversing movement by
the backlash and an
additional 180 degrees
Actual value is 180 degrees
EWA 4NEB 812 6057-02
IP 266
90