Siemens SINUMERIK 828D Function Manual page 305

F1: Travel to fixed stop
6.2 General functionality
Interrupts
If the fixed stop position is not reached when the function is active, alarm 20091 "Fixed stop not reached" is
output and a block change executed.
If a travel request (e.g. from the part program, the PLC, from compile cycles or from the operator panel front) is
provided for an axis after the fixed stop has been reached, the alarm 20092 "Travel to fixed stop still active" is
output and the axis is not moved.
If an axis has reached the fixed stop and is then moved out of this position by more than the value specified in
SD FIXED_STOP_WINDOW (Fixed stop monitoring window)
from the position, then the alarm 20093 "Standstill monitoring has triggered at the stop" is given, the function
"Travel to fixed stop" for this axis is deselected and the system variable is set $AA_FXS[x]=2.
No termination during alarm
"Travel to fixed stop" remains active from now on for alarms,
if the bit values in the machine data:
MD37052 $MA_FIXED_STOP_ALARM_REACTION
were set.
IS "Mode group ready" (DB11, ... DBX6.3) remains active.
Alarm suppression after new programming
Travel to fixed stop can be used for simple measuring processes.
For example, it is possible to carry out a check for tool breakage by measuring the tool length by traversing onto
a defined obstacle. To do so, the fixed stop alarm must be suppressed. When the function for clamping
workpieces is then used "normally," the alarm can be activated using parts program commands.
Sequence in case of a fault or abnormal termination
The IS DB31, ... DBX62.4 ("Activate travel to fixed stop") is reset.
Depending on the machine data:
MD37060 $MA_FIXED_STOP_ACKN_MASK
the acknowledgement of the PLC is awaited through resetting of the NST
DB31, ... DBX3.1 ("Enable travel to fixed stop").
The torque limitation is then canceled and a block change executed.
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 foreseen where the axis will be after deselection.
The torque limitation and monitoring of the fixed stop monitoring window are canceled.
The IS DB31, ... DBX62.4 ("Activate travel to fixed stop") and DB31, ... DBX62.5 ("Fixed stop reached") are reset.
Basic Functions
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Function Manual, 09/2011, 6FC5397-0BP40-2BA0