Siemens Sinumerik 840D sl Programming Manual page 91

Further information
Calculation of the spindle speed
The ENS position of the face axis (radius) is the basis for calculating the spindle speed from
the programmed cutting rate.
Note
Frames between WCS and SZS (e.g. programmable frames such as SCALE, TRANS or ROT)
are taken into account in the calculation of the spindle speed and can bring about a change
in speed (for example, if there is a change in the effective diameter in the case of SCALE).
Speed limitation LIMS
If a workpiece that varies greatly in diameter needs to be machined, it is advisable to specify
a speed limit for the spindle with LIMS (maximum spindle speed). This prevents excessively
high speeds with small diameters. LIMS is only applied when G96, G961, and G97 are active.
LIMS is not applied when G971is selected. On loading the block into the main run, all
programmed values are transferred into the setting data.
Note
The speed limits changed with LIMS in the part program are taken into the setting data and
therefore remain saved after the end of program.
However, if the speed limits changed with LIMS are no longer to apply after the end of program,
the following definition must be inserted in the GUD block of the machine manufacturer:
REDEF $SA_SPIND_MAX_VELO_LIMS PRLOC
Deactivating the constant cutting rate (G97/G971/G973)
After G97/G971, the control interprets an S value as a spindle speed in rpm again. If you do
not specify a new spindle speed, the last speed set with G96/G961 is retained.
The G96/G961 function can also be deactivated with G94 or G95. In this case, the last speed
programmed S... is used for subsequent machining operations.
G97 can be programmed without G96 beforehand. The function then has the same effect as
G95; LIMS can also be programmed.
Using G973, the constant cutting rate can be deactivated without activating a spindle speed
limitation.
Note
The transverse axis must be defined in machine data.
Rapid traverse G0
With rapid traverse G0, there is no change in speed.
Exception:
Fundamentals
Programming Manual, 01/2015, 6FC5398-1BP40-5BA2
7.3 Constant cutting rate (G96/G961/G962, G97/G971/G972, G973, LIMS, SCC)
Spindle motion
91