Siemens SINUMERIK 840D sl Function Manual page 43

Figure 2-3
Drives with analog setpoint interface
A drive with an analog setpoint interface is capable of traversing the machine axis with an
external setpoint. If "follow-up mode" is set for the machine axis, the actual position continues
to be acquired. Once follow-up mode has been cancelled, referencing is not required.
The following procedure is recommended:
1. Activate follow-up mode:
DB31, ... DBX2.1 = 0 (controller enable)
DB31, ... DBX1.4 = 1 (follow-up mode) (in the same or preceding OB1 cycle)
→ The axis/spindle is operating in follow-up mode
2. Deactivate external controller enable and external speed setpoint
→ Axis/spindle moves with external setpoint
→ NC continues to detect the actual position and corrects the set position to the actual
position
3. Deactivate external controller enable and cancel external speed setpoint
→ Axis/spindle stops
4. Cancelling follow-up mode
DB31, ... DBX2.1 = 1 (controller enable)
DB31, ... DBX1.4 = 0 (follow-up mode)
→ NC synchronizes to actual position. The next traversing motion begins at this position.
Note
"Follow-up mode" does not have to be cancelled because it only has an effect in
combination with "controller enable".
Cancelling follow-up mode
Once follow-up mode has been cancelled, the machine axis does not have to be referenced
again if the maximum permissible encoder limit frequency of the active measuring system was
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Trajectory for clamping and "follow-up"
A2: Various NC/PLC interface signals and functions
2.2 NC/PLC interface signals - only 840D sl
43