Siemens SINUMERIK 840C - Manual (Page 1024)

12.93 12 Functional Descriptions
12.24.5 Travel to fixed stop with programmable clamping torque
Hardware connections:
Actua-
tor
20
22
56
96
14
Speed
controller Current
setpoint
limitation Current
controller
Sensor
(optional)
I
act
NC
PLC
Position
actual
value
Speed
setpoint
M T P
Change-
over
sp./curr.
24
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.
The PLC must then activate the current limitation in the actuator (terminal 96) and transmit an
edge signal ACKNOWLEDGEMENT TRAVEL TO FIXED STOP ACTIVE to the NC.
The axis then approaches the target position at the programmed velocity.
As soon as the axis reaches 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 begins to output the current setpoint defined in NC MD 1144*.
The NC outputs the interface signal FIXED STOP REACHED to the PLC.
The PLC then activates terminal 22 of the actuator, thus effecting a switchover from speed-
controlled to current-controlled operation. After a time period of > 10 ms, the PLC switches off
the current limitation (terminal 96). In addition, the PLC also sends an edge signal
ACKNOWLEDGEMENT FIXED STOP REACHED to the NC.
The NC subsequently deletes the remaining distance to go and switches the axis to follow-up
mode.
The axis setpoint output now outputs the current setpoint in accordance with the specified
torque (SD 320*).
A block change is then performed. The current setpoint, and thus also the clamping torque,
remain applied.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 12–249
SINUMERIK 840C (IA)