Siemens SINUMERIK 840Di Function Manual page 353

In addition, the acceleration is automatically reduced in the NC according to the value in the
machine parameter:
MD37070 FIXED_STOP_ANA_TORQUE.
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 parameter:
MD37030 FIXED_STOP_THRESHOLD
is exceeded or the IS signal
"Sensor fixed stop" (DB31, ... DBX1.2) is set,
the 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 parameter:
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.
As a result, the torque now takes effect on the drive from the machine parameter:
MD37070 FIXED_STOP_ANA_TORQUE.
If the machine parameter:
MD37060 FIXED_STOP_ACKN_MASK
is set accordingly, then the IS waits for acknowledgment by the PLC in the form of IS
"Acknowledge fixed stop reached" (DB31, ... DBX1.1) and then suddenly transfers the
required clamping torque from the selection block to the drive.
A block change is executed. The clamping torque continues to be applied.
Fixed stop is not reached
If the programmed end position is reached without the "fixed stop reached" status being
recognized, then the internal torque limit in the machine parameter:
MD37070 FIXED_STOP_ANA_TORQUE
is cancelled and the IS signal "activate travel to fixed stop"
(DB31, ... DBX62.4).
The PLC must then deactivate the current limitation (terminal 96).
Travel to Fixed Stop (F1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed Description
2.3 Travel to fixed stop with analog drives
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