Siemens SINUMERIK 840D Function Manual page 737

A spindle position actual value encoder is not required for M3/M4/M5 in connection with:
● Inverse-time feedrate coding (G93)
● Feedrate in mm/min or inch/min (G94)
● Tapping with compensating chuck (G63)
Speed control mode
Speed control mode is particularly suitable if a constant spindle speed is required, but the
position of the spindle is not important (e.g. constant milling speed for even appearance of the
workpiece surface).
● Speed control mode is activated in the part program with M3, M4, M5 or with SPCOF.
● The following NC/PLC interface signal is set:
DB31, ... DBX84.7 (control mode)
● NC/PLC IS:
DB31, ... DBX61.5 (position controller active)
is reset if position control is not used.
● Acceleration in speed control mode is defined independently of the gear stage in the
machine data:
MD35200 $MA_GEAR_STEP_SPEEDCTRL_ACCEL
The value should reflect the physical circumstances, if possible.
Position control mode
Position control is particularly suitable if the position of the spindle needs to be tracked over a
longer period or if synchronous spindle setpoint value linkage is to be activated.
● Position control mode is switched on in the part program with: SPCON(<spindle
number>)
● The following NC/PLC interface signal is set:
DB31, ... DBX61.5 (position controller active)
● Acceleration in position control mode is defined independent of the gear stage in the
machine data:
MD35210 $MA_GEAR_STEP_POSCTRL_ACCEL
Independent spindle reset
The spindle response after a reset or the end of the program (M2, M30) is set with the machine
data:
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
S1: Spindles
18.2 Operating modes
737