Siemens SINUMERIK 840Di Function Manual page 331

Deselection
The NC recognizes the function deselection via programming of the command FXS[x]=0.
Then an advance stop (STOPRE) is internally released, since it can't be forseen where the
axis will be after deselection.
The torque limitation and the monitoring of the fixed stop monitoring window is cancelled.
The IS "Activate travel to fixed stop" (DB31, ... DBX62.4) and "Fixed stop reached"
(DB31, ... DBX62.5) are reset.
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/or
"Acknowledge fixed stop reached" (DB31, ... DBX1.1).
The axis will then change to position control. The followup mode of the position setpoints is
ended and a synchronization to the new actual position is carried out.
A programmed traverse motion can then be executed. This motion must lead away from the
fixed stop or else the stop or even the machine may sustain damage.
A block change is executed after the target position has been reached.
Multiple selection
A selection may only be carried out once. If the function is called once more due to faulty
programming (FXS[Axis]=1) the alarm 20092 "Travel to fixed stop still active" is initiated.
Blockrelated synchronized actions
By programming a blockrelated synchronized action, travel to fixed stop can be connected
during an approach motion.
Programming example:
N10 G0 G90 X0 Y0
N20 WHEN $AA_IW[X]>17 DO FXS[X]=1
N30 G1 F200 X100 Y110
Changing the clamping torque and fixed stop monitoring window
The clamping torque and the monitoring window can be changed with the commands
FXST[x] and FXSW[x]. The changes take effect before traversing movements in the same
block.
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.
Travel to Fixed Stop (F1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
2.1 General functionality
; If X reaches a position greater
; 17mm FXS is activated
Detailed Description
2-7