Siemens SINUMERIK 840Di Function Manual page 352

Detailed Description
2.3 Travel to fixed stop with analog drives
Fixed clamping torque
A fixed current limitation is preset in the drive actuator by means of a resistor circuit (or via
R12). This current limitation is activated by the control via a PLC output (which acts on
terminal 96 of the actuator), thus ensuring that a fixed clamping torque is available on the
axis.
Setpoints can be injected via terminals 56/14 or 24/20.
Programmable clamping torque
In this case, the PLC switches the drive actuator from speed-controlled into current-
controlled operation as soon as the fixed stop is reached.
Activation of terminal 22 causes the voltage level applied to terminals 20/24 to take effect as
a current setpoint rather than a speed setpoint.
The NC is thus able to specify a variable clamping torque.
Setpoints must be injected via terminals 24/20.
References:
/IAA/ Installation and start-up guide SIMODRIVE 611 analog system
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 parameter:
MD37060 FIXED_STOP_ACKN_MASK
is set accordingly, then the IS waits for acknowledgment by the PLC in the form of IS
"Activate travel to fixed stop" (DB31, ... DBX3.1)
and then 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.
The NC then internally sets the torque limit to the value specified via the machine parameter:
MD37070 FIXED_STOP_ANA_TORQUE
(torque limit on fixed stop approach for analog drives).
This value must correspond to the torque limit value activated via terminal 96.
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Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Travel to Fixed Stop (F1)