Siemens SINUMERIK 840D Function Manual page 878

S3: Synchronous spindle
19.4 Special features
Controller enable (DB31, ... DBX2.1)
LS: Resetting the "controller enable" during synchronous operation
If the controller enable of the LS is reset during synchronous operation for active setpoint
coupling, a control-internal switching is made to the actual value coupling. If the controller
enable is reset while the LS is traversing, the LS is stopped and an alarm issued. Synchronous
operation remains active.
LS and FS: Selection of synchronous operation without controller enable
If the "controller enable" for LS and FS is not set for selected synchronous operation, it will be
activated. LS and FS, however, are not traversed until controller enable for LS and FS has been
granted.
LS and FS: Setting the "Controller enable"
The position assumed by a spindle with setting the "controller enable" depends on DB31, ...
DBX1.4 == <value> (follow-up operation):
<value> Assumed spindle position
Note
It is recommended for synchronous spindles during a block search, to write the DB31, ...
DBX2.1 interface signal (controller enable) always together for FS and LS. If this is not done,
the block search, for example, stops after a FS machining because the controller enable of the
LS is not pending.
Note
Synchronism error
If the DB31, ... DBX2.1 interface signal (controller enable) is canceled for the FS after Spindle
Stop without the coupling being deactivated beforehand, then any synchronism error resulting
from external intervention will not be compensated when the "controller enable" is activated
again. This causes any programmed angular relationship between FS and LS to be lost.
The angular relationship can be restored by resynchronizing: DB31, ... DBX31.4 = 1
(resynchronization)
Follow-up mode (DB31, ... DBX1.4)
For follow-up operation, the set position is regularly set to the current actual position:
DB31, ... DBX1.4 == 1 (follow-up operation) AND DB31, ... DBX2.1 == 0 (controller enable)
878
0 Position when controller enable is canceled
1 Current position
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA