Siemens SINUMERIK 828D Function Manual page 303

Fixed stop reached
As soon as the axis comes into contact with the mechanical fixed stop (workpiece), the closed­loop 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 "Fixed point reached" status can be calculated as follows depending on the machine data:
MD37040 $MA_FIXED_STOP_BY_SENSOR (fixed stop recognition by sensor)
:
• FIXED_STOP_BY_SENSOR = 0
The "Fixed stop reached" status is achieved when the axial contour deviation (= difference between actual
and expected following error) has exceeded the value set in machine data:
MD37030 $MA_FIXED_STOP_THRESHOLD (Threshold for fixed stop detection)
has exceeded.
• FIXED_STOP_BY_SENSOR = 1
External sensor transmits the "Fixed stop reached" state to the NC via the PLC using the IS DB31, ... DBX1.2
("Sensor fixed stop").
• FIXED_STOP_BY_SENSOR = 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).
The axis contour deviation is explained in:
References:
/FB1/ Function Manual Basic Function; Diagnostics tool (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 using IS DB31, ... DBX62.5 ("Fixed stop reached").
If the machine data:
MD37060 $MA_FIXED_STOP_ACKN_MASK
is set correspondingly, then the system waits for the acknowledgement of the PLC using the IS DB31, ... DBX1.1
("Acknowledge fixed stop reached").
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.
Monitoring window
If no fixed stop monitoring window was programmed in the block or from program start, then the value set in the
machine data:
MD37020 $MA_FIXED_STOP_WINDOW_DEF
(Default for fixed stop-monitoring window)
is entered.
If the axis leaves the position it was in when the fixed stop was detected, then alarm 20093 "Fixed stop
monitoring has responded" is displayed and the "Travel to fixed stop" function deselected.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
F1: Travel to fixed stop
6.2 General functionality
303