Siemens SINUMERIK 840D sl Function Manual page 791

Actual-value reading
If the actual value of $AA_IW is read in the WCS after activation of a frame (zero offset) or a
tool offset, the activated changes are already contained in the result read even if the axes have
not yet been traversed with the activated changes.
The actual values in the settable zero system (SZS) can be read from the part program for
each axis using the variable $AA_IEN[axis].
The actual values in the basic zero system (BZS) can be read from the part program for each
axis using the variable $AA_IBN[axis].
Actual-value display
The programmed contour is always displayed in the WCS.
The following offsets are added to the MCS:
● Kinematic transformation
● DRF offset/zero offset external
● Active frame
● Active tool offset of the current tool
Switchover by PLC
The actual values can be displayed in the WCS, SZS, BZS or MCS via the PLC. The PLC can
define, which coordinate system corresponds to the workpiece coordinate system on a
machine.
On MMC power-up the MCS is preset.
With the signal DB19 DBB0.7 "MCS/WCS switchover", it is also possible to switch from the
PLC to the WCS.
Transfer to PLC
Depending on machine data
MD20110 / MD20112, bit 1
, the auxiliary functions (D, T, M) are output to the PLC (or not) on selection of the tool length
compensation.
Note
If the WCS is selected from the PLC, an operator action can still be used to switch between
the WCS and MCS for the relevant mode.
However, when the mode and or area is changed, the WCS selected by the PLC is evaluated
and activated (see Section "K1: Mode group, channel, program operation, reset response
(Page 455)").
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
K2: Axis Types, Coordinate Systems, Frames
10.6 Workpiece-related actual value system
791