Siemens SINUMERIK 840D Function Manual page 783

The programmed spindle speed (S...) then refers to this permanently defined gear stage:
● If a spindle speed is programmed and it is higher than the maximum speed of the
permanently defined gear stage (MD35130 $MA_GEAR_STEP_MAX_VELO_LIMIT), then
the speed is decreased to this limit and the following NC/PLC interface signal is set:
DB31, ... DBX83.1 (speed setpoint limited)
● If a spindle speed is programmed and it is lower than the minimum speed of the permanently
defined gear stage (MD35140 $MA_GEAR_STEP_MIN_VELO_LIMIT), then the speed is
increased to this minimum and the following NC/PLC interface signal is set:
DB31, ... DBX83.2 (speed setpoint increased)
Block change
When programming the gear stage change in the part program, the gear stage change set
remains active until it is aborted by PLC.
This corresponds to the effect as if the following NC/PLC interface signal were set:
DB21, ... DBX6.1 (read-in disable)
Specification of gear stage via PLC with FC18
The gear stage change can also be performed by function block FC18 during a part program,
in the reset state or in all operating modes.
If the speed and direction of rotation is specified with FC18, the NC can be requested to select
the gear stage as appropriate for the speed. This corresponds to an automatic gear stage
change with M40.
The gear stage is not changed if:
● The spindle is positioned via FC18.
● The spindle is traversed in the axis mode.
Further information
For further information on the FC18 function block, see Function Manual PLC.
Specification of a gear stage in synchronized actions
The gear stage change can be requested by synchronized actions using:
● DO M40 S...
Automatic gear stage selection to the programmed speed S...
● DO M41... M45
Direct selection of gear stages 1 ... 5
● DO M70
For MD35014 $MA_GEAR_STEP_USED_IN_AXISMODE = 1 ... 5
(see "Configurable gear step in M70 (Page 805)")
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
S1: Spindles
18.4 Configurable gear adaptations
783