Siemens SINUMERIK 840C - Manual (Page 1031)

12 Functional Descriptions 12.93
12.24.7 Diagrams for selection/deselection of travel to fixed stop
12.24.7.5 Travel to fixed stop with digital drives
(SIMODRIVE 611D MSD/FDD)
The functional sequence for digital drives is basically the same as that for analog drives.
However, digital drives do not have external terminal wiring or any resistor circuitry in the drive.
The handling of PLC signals is also simpler in digital drive systems.
Functional sequence
The NC detects selection of function G221 (via G function or command channel) during block
processing and informs the PLC that the function has been selected via the interface signal
TRAVEL TO FIXED STOP ACTIVE. At the same time, the current limitation is activated at a
value corresponding to that set in NC MD 1144* (switchover current setpoint).
The axis then approaches the target position at the programmed velocity.
As soon as the axis has reached the fixed stop, the following error increases. As a result of
the increase in the following error above the threshold set in NC MD 1280* or owing to the
input signal of a sensor (which is passed on to the PLC-NC interface), the control detects that
the fixed stop has been reached.
The NC setpoint interface then specifies a clamping torque according to the programmed (P...)
or the value set in SD 320*.
The NC outputs the interface signal FIXED STOP REACHED to the PLC.
The NC subsequently deletes the remaining distance-to-go and switches the axis to the ”travel
to fixed stop active” status.
A block change is then performed. The current setpoint, and thus also the clamping torque,
remain applied.
Note:
Spindles must be switched to C-axis mode before the travel to fixed stop function is selected.
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SINUMERIK 840C (IA)