Siemens SINUMERIK 802D sl Function Manual page 354

Spindle (S1)
20.4 Gear stage change
M41 to M45
The gear stage can be permanently defined in the part program with M41 to M45. If a gear
stage is defined by M41 to M45, which is different than the current (actual) gear stage, the IS
"Change gear" (V390x 2000.3) and the IS "Set gear stage A" to "...C" (V390x 2000.0 to .2)
are set. The programmed spindle speed (S) then refers to this permanently defined gear
stage. If a spindle speed exceeding the maximum speed of the permanently defined gear
stage is programmed, the speed is limited to the maximum speed of this gear stage and the
IS "Programmed speed too high" (V390x 2001.1) is enabled. If a speed is programmed lower
than the minimum speed of this gear stage, the speed is raised to this speed. The IS
"Setpoint speed increased" (V390x 2001.2) is then enabled.
M40
M40 in the part program causes the gear stage to be selected automatically by the control.
The control checks which gear stage is possible for the programmed spindle speed (S
function). If the suggested gear stage is not equal to the current (actual) gear stage, the IS
"Change gear" (V390x 2000.3) and the IS "Set gear stage A to C" (V390x 2000.0 to .2) are
enabled.
The automatic gear stage selection function initially compares the programmed spindle
speed with the minimum and maximum speed of the current gear stage. If the comparison is
positive, a new gear stage is not defined. If the comparison is negative, the comparison is
performed on each of the gear stages (starting with gear stage 1) until the result is positive. If
the comparison in the 5th gear stage is also not positive, no gear stage change is triggered.
If necessary the speed is limited to the maximum speed of the current gear stage or
increased to the minimum speed of the current gear stage, and the IS "Setpoint speed
limited" (V390x 2001.1) or IS "Setpoint speed increased" (V390x 2001.2) is enabled.
Figure 20-7
354
Example for speed ranges for automatic gear stage selection (M40)
Turning, Milling, Nibbling
Function Manual, 11/2012, 6FC5397-1CP10-5BA0