Siemens SINUMERIK 840D Function Manual page 781

The speed limitations are configured only once for each gear stage with the following machine
data, independently of the different switching thresholds:
Machine data
MD35130 $MA_GEAR_STEP_MAX_VELO_LIMIT[n]
MD35140 $MA_GEAR_STEP_MIN_VELO_LIMIT[n]
For tapping without compensating chuck (G331, G332) the speed can be limited to the linear
acceleration range of the motor additionally. For this, the maximum speed of the linear motor
characteristics range is specified in the following machine data as a function of the gear stage:
MD35550 $MA_DRILL_VELO_LIMIT[n]
Specify gear stage in the part program
Automatic selection with active M40
The gear stage is automatically selected by the control. The gear stage in which the
programmed spindle speed (S...) is possible is checked in this context. If a gear stage results
from this that is not equal to the current (actual) gear stage, then the following NC/PLC interface
signals are set:
DB31, ... DBX82.3 (change over gear stage)
DB31, ... DBX82.0-82.2 (setpoint gear stage A to C)
While the appropriate gear stage is being determined, a gear stage change is only requested
if the new speed is not within the permissible speed range of the active gear stage.
The speed is limited to the maximum speed of the current gear stage or raised to the minimum
speed of the current gear stage and the appropriate NC/PLC interface signal is set:
DB31, ... DBX83.1 (speed setpoint limited)
DB31, ... DBX83.2 (speed setpoint increased)
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
18.4 Configurable gear adaptations
Meaning
Maximum speed of gear stage
Minimum speed of gear stage
S1: Spindles
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