Siemens SINUMERIK 840D sl Function Manual page 125

$AA_IW[ ] and $AA_IB[ ] are changed. These variables now contain the deselected share of
tool length compensation.
Once "Online tool length offset" has been deselected for a tool direction, the value of system
variable $AA_TOFF[ ] or $AA_TOFF_VAL[ ] is zero for this tool direction. The following interface
signal is set to 0:
DB21, ... DBX318.2 (TOFF active)
Alarm 21670
An existing tool length offset must be deleted via TOFFOF( ) so that alarm 21670 "Channel
%1 block %2, illegal change of tool direction active due to $AA_TOFF active" is suppressed:
● When the transformation is deactivated with TRAFOOF
● On switch-over from CP to PTP travel.
● If a tool length offset exists in the direction of the geometry axis during geometry
replacement.
● If a tool length offset is present during change of plane.
● When changing from axis-specific manual travel in JOG mode to PTP as long as a tool
length compensation is active. There is no switchover to PTP.
Mode change
Tool length compensation remains active even if the mode is changed and can be executed
in any mode.
If a tool length compensation is interpolated on account of $AA_TOFF[ ] during mode change,
the mode change cannot take place until the interpolation of the tool length compensation has
been completed. Alarm 16907 "Channel %1 action %2 ALNX possible only in stop state" is
issued.
Behavior with REF and block search
Tool length offset is not considered during reference point approach REF in JOG mode.
The instructions TOFFON( ) and TOFFOF( ) are not collected and output in an action block
during block search.
System variable
In the case of online tool length offset, the following system variables are available to the user:
System variable
$AA_TOFF[ ]
$AA_TOFF_VAL[ ]
$AA_TOFF_LIMIT[ ]
$AA_TOFF_PREP_DIFF[ ]
Special functions
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
Meaning for online tool length offset
Position offset in the tool coordinate system
Integrated position offset in the WCS
Query whether the tool length offset value is close to the limit
Magnitude of the difference between the currently active value of
$AA_TOFF[ ] and the value prepared as the current motion block.
F2: Multi-axis transformations
2.12 Online tool length offset
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