Siemens SINUMERIK 840Di Function Manual page 356

Detailed Description
2.3 Travel to fixed stop with analog drives
The speed controller forces the drive to the torque 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 parameter) 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 one of the programmable terminals E1-E9 (e.g.
terminal E5) and switches off the torque limitation after a period of 80 ms by selecting the
preceding gear stage.
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_ASK
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 detected,
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 then activates the preceding gear stage, thus deactivating the torque limitation. It
also switches on the speed control monitoring function again.
Depending on the machine parameter:
MD37060 FIXED_STOP_ACKN_MASK
the NC waits for the PLC to acknowledge by resetting IS
"Activate travel to fixed stop" (DB31, ... DBX3.1)
and then the block change is performed.
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Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Travel to Fixed Stop (F1)