Siemens SINUMERIK 840Di Function Manual page 121

Positioning axes
For positioning axes, only the programmed block end point is monitored.
An alarm is displayed during the traversing motion of the positioning axes:
Alarm: " 10704 Protection zone monitoring is not guaranteed"
Axis exchange
If an axis is not active in a channel because of an axis replacement, the position of the axis
last approached in the channel is taken as the current position. If this axis has not yet been
traversed in the channel, zero is taken as the position.
Machine-related protection zones
A machine-related protection zone or its contour is defined using the geometry axis, i.e. with
reference to the basic coordinate system (BCS) of a channel. In order that correct protection
zone monitoring can take place in all channels in which the machine-related protection zone
is active, the basic coordinate system (BCS) of all affected channels must be identical
(position of the coordinate point of origin with respect to the machine zero point and
orientation of the coordinate axes).
Axis Monitoring, Protection Zones (A3)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Detailed Description
2.4 Protection zones
2-49