Siemens SINUMERIK 840D Function Manual page 111

Block-related activation (FOC)
The function for the actual block is activated using the FOC command.
Activating the function using a synchronized action takes effect up to the end of the current part
program block.
Priority of FXS before FOC
Activating the "Travel to fixed stop" function FXS has a higher priority than the "Force Control"
function. If "Travel to fixed stop" is active at the same time as "Force Control", then the first is
executed.
Deselecting the "Travel to fixed stop" function FXS cancels the clamping. A "Force Control"
function that is at same time permanently active, remains active.
System variable
Status of the "Force Control" function
The status of the "Force Control" function can be read using system variable $AA_FOC.
Changing the status of the "Travel to fixed stop" function FXS does not change the status of the
"Force Control" function.
$AA_FOC
Value
Status of torque limiting
The actual status of the torque limiting can be read using system variable
$VA_TORQUE_AT_LIMIT.
$VA_TORQUE_AT_LIMIT
Value
Restrictions
the "Force Control" function has the following restrictions:
● The change of the torque/force limitation representing itself as an acceleration limitation
is only taken into account in the traversing movement at block limits (see command ACC).
● Only FOC: No monitoring is possible from the NC/PLC interface to check that the active
torque limit has been reached.
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
Meaning
0 FOC not active
1 FOC modal active
2 FOC non-modal active
Meaning
0 actually effective torque < torque limit value
1 actually effective torque == torque limit value
F1: Travel to fixed stop
3.2 Detailed description
111