Siemens SINUMERIK 840Di Function Manual page 328

Detailed Description
2.1 General functionality
Fixed stop reached
As soon as the axis comes into contact with the mechanical fixed stop (workpiece), the
closed-loop control in the drive raises the torque so that the axis can move on. The torque
rises up to the programmed limit value and then remains constant.
The status "fixed stop reached" can, depending on the machine parameter:
MD37040 FIXED_STOP_BY_SENSOR (fixed stop recognitioner by sensor)
be determined in the following ways:
• FIXED_STOP_BY_SENSOR = 0
• FIXED_STOP_BY_SENSOR = 1
• FIXED_STOP_BY_SENSOR = 2
The axial contour deviation is explained in:
References:
/FB1/ Function descriptions machine basics; Diagnostic aid (D1)
Internal processes
Once the NC has detected the "Fixed stop reached" status, it deletes the distancetogo and
the position setpoint is made to follow. The controller enabling command remains active.
The PLC is then informed of the state by means of IS "Fixed stop reached"
(DB31, ... DBX62.5).
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
"Acknowledge fixed stop reached" (DB31, ... DBX1.1).
The NC then executes a block change or considers the positioning motion to be completed,
but still leaves a setpoint applied to the drive actuator to allow the clamping torque to take
effect.
The fixed stop monitoring function is activated as soon as the stop position is reached.
2-4
The status "fixed stop reached" is active when the axial contour deviation (= difference
between actual and expected following error) has exceeded the value of the machine
parameter:
MD37030 FIXED_STOP_THRESHOLD (threshold for fixed stop recognition).
External sensor transmits "Fixed stop reached" status to NC via the PLC by means of IS
"Sensor fixed stop" (DB31, ... DBX1.2).
The "Fixed stop reached" status is active either when the status has been detected by the
contour monitoring function or when the external sensor signals this status by a signal
change from 0 " 1 to (DB31,...DBX 1.2).
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Travel to Fixed Stop (F1)