Siemens SINUMERIK 840D sl Function Manual page 123

Only workpiecerelated protection zones can be enabled temporarily with NC start and
traversed by all toolrelated protection zones including the programmed path.
If on NC-START the preactivated tool or workpiecerelated protection zone is deactivated by
the PLC after the alarm, machining is continued without the protection zone being enabled
temporarily.
If a fully operative, preactivated protection zone causes a machining interruption and the
output of an alarm owing to protection-zone violation, machining can be resumed on NC start
if the PLC makes the zone inoperative again.
If enabling of a protection zone is to be safeguarded better than with a simple NC start, NC
start must be disabled or made dependent on other conditions in the PLC user program
when this alarm is triggered.
If the user does not want to permit overrunning the protection zone, he can terminate the
traversing movement with NC RESET.
If several protection zones are violated at the same time by the movement, acknowledgment
is required for each of these protection zones. With NC start the individual protection zones
can then be enabled one after the other.
Application for temporary enabling:
Drilling a turned part: The drill is allowed to enter the protection zone of the spindle chuck.
Monitoring of overlaid motion
On preparation of the NC blocks, part of the offsets of geometry axes resulting from the
overlaid motions are taken into account.
If further offsets occur that could not be taken into account on preparation of the blocks, the
channelspecific PLC interface signal is set.
DB31, ... DBX39.0 (protection-zone monitoring not guaranteed).
This signal is set while offsets are active that cannot be taken into account. The signal can
be set and reset within a block.
Simultaneously with the PLC interface signal, a selfcanceling alarm 10704 "Protection-zone
monitoring is not guaranteed" is output.
The following overlaid motions of geometry axes are taken into account in the preparation of
blocks:
1. DRF offsets
2. Work offsets external
3. Fine tool offsets
4. Rapid retraction
5. Offsets generated by compile cycles
6. Oscillation
7. Concurrent positioning axes
8. Positioning axes
The alarm is canceled or the PLC interface signal reset when the offsets from the overlaid
motions are taken into account again or when the offsets are reduced to zero again.
Basic logic functions: Axis monitoring, protection zones (A3)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Detailed description
2.2 Protection zones
57