Siemens SINUMERIK 840D sl Operating Manual page 76

Setting up the machine
4.5 Zero offsets
After reference point approach, the actual value display for the axis coordinates is based on
the machine zero of the machine coordinate system (Machine).
The actual value display of the positions can also refer to the SZS coordinate system (settable
zero system). The position of the active tool relative to the workpiece zero is displayed.
Figure 4-1
When the machine zero is not identical to the workpiece zero, at least one offset (base offset
or zero offset) exists in which the position of the workpiece zero is saved.
Base offset
The base offset is a zero offset that is always active. If you have not defined a base offset, its
value will be zero. The base offset is specified in the "Zero Offset - Base" window.
Settable zero system (SZS)
The SZS (Settable Zero System) corresponds to the WCS transformed by the programmable
frame (e.g. $P_PFRAME, $PCYCFRAME, $P_TOOLFRAME and $P_WPFRAME).
Basic zero system (BZS)
The BZS (Basic Zero System) includes not only the frames of the ENS, but also the current
settable frame ($P_IFRAME and $P_GFRAME).
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Zero offsets
Operating Manual, 05/2017, A5E40869190
Grinding