Siemens SINUMERIK 840D sl Programming Manual page 365

Clamping torque (FXST) and monitoring window (FXSW)
Any programmed torque limiting FXST is effective from the block start, i.e. the fixed stop is also
approached at a reduced torque. FXST and FXSW can be programmed and changed in the part
program at any time. The changes take effect before traversing movements in the same block.
NOTICE
Risk of collision
Programming of a new fixed stop monitoring window causes a change not only in the window
width, but also in the reference point for the center of the window if the axis has moved prior
to reprogramming. The actual position of the machine axis when the window is changed is the
new window center point.
The window must be selected such that only a breakaway from the fixed stop causes the fixed
stop monitoring to respond.
Further information
Rise ramp
A rate of rise ramp for the new torque limit can be defined in MD to prevent any abrupt changes
to the torque limit setting (e.g. insertion of a quill).
Alarm suppression
The fixed stop alarm can be suppressed for applications by the part program by masking the
alarm in a machine data item and activating the new MD setting with NEW_CONF.
Activation
The commands for travel to fixed stop can be called from synchronized actions or technology
cycles. They can be activated without initiation of a motion, the torque is limited
instantaneously. As soon as the axis is moved via a setpoint, the limit stop monitor is activated.
Activation from synchronized actions
Example:
If the expected event ($R1) occurs and travel to fixed stop is not yet running, FXS should be
activated for axis Y. The torque must correspond to 10% of the rated torque value. The width
of the monitoring window is set to the default.
Program code
N10 IDS=1 WHENEVER (($R1=1) AND ($AA_FXS[Y]==0)) DO $R1=0 FXS[Y]=1
FXST[Y]=10
The normal part program must ensure that $R1 is set at the desired point in time.
Deactivation from synchronized actions
Example:
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
Fundamentals
2.14 Supplementary commands
365