Siemens SINUMERIK 840D sl Function Manual page 23

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, homing is not required.
The following procedure is recommended:
1. Activate follow-up mode:
2. Deactivate external servo enable and external speed setpoint
3. Deactivate external servo enable and cancel external speed setpoint
4. Canceling followup mode
Canceling followup mode
Once follow-up mode has been canceled, the machine axis does not have to be homed
again if the maximum permissible encoder limit frequency of the active measuring system
was not exceeded during follow-up mode. If the encoder limit frequency is exceeded, the
controller will detect this:
• DB31, ... DBX60.4 / 60.5 = 0 (homed/synchronized 1 / 2)
• Alarm: "21610 Encoder frequency exceeded"
Basic logic functions: Various NC/PLC interface signals and functions (A2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
DB31, ... DBX2.1 = 0 (servo enable)
DB31, ... DBX1.4 = 1 (follow-up mode) (in the same or preceding OB1 cycle)
→ The axis/spindle is operating in followup mode
→ Axis/spindle moves with external setpoint
→ NC continues to detect the actual position and corrects the setpoint position to the
actual position
→ Axis/spindle stops
DB31, ... DBX2.1 = 1 (servo enable)
DB31, ... DBX1.4 == 0 (follow-up mode)
→ NC synchronizes to current actual position. The next traversing movement begins at
this position.
Note
"Followup mode" does not have to be canceled because it only has an effect in
combination with "servo enable".
Note
If "follow-up mode" is deactivated for a machine axis, which is part of an active
transformation (e.g. TRANSMIT), this can generate movements as part of repositioning
(REPOS) other machine axes involved in the transformation.
Detailed description
2.1 NC/PLC interface signals
17