Siemens SINUMERIK 840D sl Function Manual page 376

Detailed Description
2.3 Travel to fixed stop with analog drives
Subsequently the controller internally sets the torque limit to the value specified through the
machine data: MD37070 FIXED_STOP_ANA_TORQUE (Torque limit while approaching the
fixed stop for analog drives).
This must correspond to the torque limit value set in the actuator.
In addition, the acceleration is automatically reduced in the NC according to the value in the
machine data: MD37070 FIXED_STOP_ANA_TORQUE is reduced.
The rotary axis now traverses to the target position at the programmed velocity.
Fixed stop reached
As soon as the Caxis reaches the fixed stop, the axial contour deviation increases.
If in the machine data:
MD37030 FIXED_STOP_THRESHOLD
entered threshold is exceeded or the NST signal
"sensor fixed stop" (DB31, ... DBX1.2) is set,
the control system detects that the fixed stop has been reached.
The position controller then responds by outputting a speed setpoint, corresponding to the
value set in the machine data: MD37070 FIXED_STOP_ANA_TORQUE
The speed controller forces the drive to the torque limit by means of this continuously applied
setpoint.
The NC then deletes the remaining distancetogo and forces the position setpoint to follow.
The controller enabling command remains active.
The NC then outputs IS "Fixed stop reached" (DB31 , ... DBX62.5) to the PLC.
If a programmable clamping torque input (via FXST[x] or setting parameter) is required
from the NC, then the PLC must switch the drive over from speed controlled to current
controlled operation. To do so, it activates one of the programmable terminals E1 - E9 (e.g.
terminal E5) and switches off the torque limitation after a period of > 80 ms by selecting the
previous gear stage.
The torque set in machine data:
MD37070 FIXED_STOP_ANA_TORQUE
acts on the drive.
If the machine data:
MD37060 FIXED_STOP_ACKN_ASK
is set correspondingly, the acknowledgement of the PLC via the NST
("Acknowledge fixed stop reached") (DB31, ... DBX1.1) is awaited and then the requested
clamping torque is transferred from the select block to the drive steplike.
Then a block change is executed. The clamping torque continues to be applied.
40
Basic logic functions: Travel to fixed stop (F1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0