Siemens SINUMERIK Series Function Manual page 741

Display differential speed
The programmed difference component is displayed as the speed setpoint for the
programmed differential speed (in our example, corresponds to 100 rpm).
The actual speed refers to the motor speed. In the example, the actual speed is 500 rev/min
* (-1) + 100 rpm = -400 rev/min.
IS NCK to PLC
Following spindle in speed-controlled operation
The IS "Spindle in setpoint range" (DB31, ... DBX83.5) is set for the following spindle by the
NCK if the programmed speed difference (see previous example, N26 with M2=3 S2=100) is
reached. If a differential speed is programmed and not enabled by the PLC, this VDI
interface signal is not set.
Even if a differential speed has been programmed, the following spindle remains under
position control if this is required by the coupling.
Note
The axial VDI interface signal NCK → PLC IS "Superimposed motion" (DB31, ... DBX98.4) is
set when the differential speed programming creates setpoints in addition to the coupling
setpoints.
Actual direction of rotation clockwise (DB31, ... DBX83.7)
IS "Actual direction of rotation clockwise" (DB31, ... DBX83.7) refers to the resulting motor
direction.
IS PLC to NCK
Influence on following spindle via PLC interface
The effect of the axial VDI interface signals on the following spindle with differential speed in
speed control mode is described below.
Delete distance to go / Spindle Reset (DB31, ... DBX2.2)
The programmed differential speed and direction can be terminated by IS "Delete distance-
to-go / Spindle Reset" (DB31, ... DBX2.2). To delete the programmed speed only, it is
possible to set IS "Delete S value" (DB31, ... DBX16.7).
Resynchronize spindle 1/2 (DB31, ... DBX16.4 and 16.5)
The IS "Resynchronize spindle 1/2" (DB31, ... DBX16.4/16.5) are not locked. Any positional
offset is not compensated automatically by the coupling.
Extended Functions
Function Manual, 03/2013, 6FC5397-1BP40-3BA1
S3: Synchronous spindle
13.4 Points to note
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