Siemens SINUMERIK 840Di Function Manual page 826

Detailed Description
2.4 Frames
If a level change of the axis signal from 0 to 1 is detected, the movement is stopped
immediately, the preprocessing is reorganized and the current system frame is written and
activated with the axis value of $AA_ETRANS[axis]. The system frame in the data
management is also described. The offset is then first applied and the interrupted motion is
continued.
With G91 and machine data setting
MD42440 $MC_FRAME_OFFSET_INCR_PROG = 0,
the zero offset external is also applied with the approach block.
Special treatment when programming incrementally is not relevant for the zero offset
external. Activation always leads to the offset being applied immediately.
The zero offset external acts on the absolute translation absolutely (coarse offset) of the
current system frame. Therefore, a multiple activation of a zero offset external does not act
additively, and only the coarse component of the translation is overwritten with the value
$AA_ETRANS[axis]. The current system frame is the system frame currently active in the
main run.
2.4.9.3 Toolholder
Translations
With kinematics of type P and M the selection of a toolholder activates an additive frame
(table offset of the orientational toolholder), which takes into account the zero point offset as
a result of the rotation of the table.
The zero offset is entered into a system frame ($P_PARTFR).
The translational part of this frame is then overwritten.
Other contents of the frame are left unchanged.
In order to be able to use this system frame, bit 2 must be set in the machine data
MD28082 $MC_MM_SYSTEM_FRAME_MASK.
Alternatively, there is the option to enter this offset into the basic frame identified by machine
data
MD20184 $MC_TOCARR_BASE_FRAME_NUMBER.
This option is available in the interests of compatibility with older software versions.
It is not recommended for use with new systems.
A frame offset as a result of a toolholder change becomes effective immediately on selection
of TCARR=.... A change in the tool length, on the other hand, only becomes effective
immediately if a tool is active.
A frame rotation does not take place on activation and a rotation which is already active is
not changed. As in case T (only the tool can be rotated), the position of the rotary axes used
for the calculation is dependent on the G code TCOFR/TCOABS and determined from the
rotation component of an active frame or from the entries $TC_CARRn. Activation of a frame
changes the position in the workpiece coordinate system accordingly, without compensating
movement by the machine itself.
2-96
Axis Types, Coordinate Systems, Frames (K2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0