Siemens Sinumerik 840D sl Programming Manual page 456

Tool offsets
7.10 Online tool length compensation (TOFFON, TOFFOF)
Further information
Block preparation
During block preparation in preprocessing, the current tool length offset active in the main run
is also taken into consideration. To allow extensive use to be made of the maximum
permissible axis velocity, it is necessary to stop block preparation with a STOPRE
preprocessing stop while a tool offset is established.
The tool offset is always known at the time of run-in when the tool length offsets are not
changed after program start or if more blocks have been processed after changing the tool
length offsets than the IPO buffer can accommodate between run-in and main run.
Variable $AA_TOFF_PREP_DIFF
The dimension for the difference between the currently active compensation in the
interpolator and the compensation that was active at the time of block preparation can be
polled in the variable $AA_TOFF_PREP_DIFF[<n>].
Adjusting machine data and setting data
The following system data is available for online tool length offset:
• MD20610 $MC_ADD_MOVE_ACCEL_RESERVE (acceleration margin for overlaid
motion)
• MD21190 $MC_TOFF_MODE
Content of system variable$AA_TOFF[<n>] is moved through as absolute value or is
integrated up.
• MD21194 $MC_TOFF_VELO (velocity of the online tool length compensation)
• MD21196 $MC_TOFF_ACCEL (acceleration of the online tool length compensation)
• Setting data for presetting limit values:
SD42970 $SC_TOFF_LIMIT (upper limit of the tool length compensation value)
Reference:
Function Manual, Special Functions; F2: Multi-axis transformations
456
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
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