Siemens SINUMERIK 840D sl Function Manual page 373

Selection
The NC detects that the function "travel to fixed stop" is selected via the command
FXS[x]=1 and signals the PLC via the IS "Activate travel to fixed stop" (DB31, ... DBX62.4)
that the function has been selected.
The PLC must then activate the current limitation on the actuator (terminal 96).
If the machine data:
MD37060 FIXED_STOP_ACKN_MASK
is set correspondingly, the acknowledgement of the PLC via the NST
"Enable travel to fixed stop" (DB31, ... DBX3.1) awaited
and after that the function is started.
Note
(This acknowledgment should always be programmed for analog drives for safety reasons,
i.e. so that the motion is not started before the torque has been limited).
Subsequently the NC internally sets the torque limit on the value specified via the machine
data: MD37070 FIXED_STOP_ANA_TORQUE (Torque limit while approaching the fixed stop
for analog drives).
This must correspond to the torque limit value activated via terminal 96.
In addition, the acceleration is automatically reduced in the NC according to the value in the
machine data: MD37070 FIXED_STOP_ANA_TORQUE is automatically reduced.
The axis now traverses to the target position at the programmed velocity.
Fixed stop reached
As soon as the axis reaches the fixed stop, the axial contour deviation increases.
If the recorded threshold in the machine data: MD37030 FIXED_STOP_THRESHOLD is
exceeded or the NST signal "sensor fixed stop" (DB31, ..DBX1.2) is set, he controller
recognizes that the fixed stop has been reached.
The position controller then responds by outputting a speed setpoint, corresponding to the
value set in the machine data: MD37070 FIXED_STOP_ANA_TORQUE
The speed controller's output is limited by terminal 96, forcing the drive to the current limit by
means of this continuously applied setpoint.
The NC then deletes the remaining distancetogo and forces the position setpoint to follow.
The controller enabling command remains active.
The NC then outputs IS "Fixed stop reached" (DB31 , ... DBX62.5) to the PLC.
If a programmable clamping torque input (via FXST[x] or setting data), is required from the
NC, then the PLC must switch the drive over from speed controlled to current controlled
operation.
To do so, it activates terminal 22 and switches off the current limitation (terminal 96) after a
period of 10 ms.
Basic logic functions: Travel to fixed stop (F1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed Description
2.3 Travel to fixed stop with analog drives
37