Siemens SINUMERIK 840C - Manual (Page 915)

12 Functional Descriptions 10.94
12.18.8 Following drive overlays
The overlay path FD is calculated on the basis of the present actual positions and the
specified synchronous positions; this path is then transferred to the following drive as an
incremental overlay path.
FD= (FD
syn
- FD
act
) + KF1*(LD1
act
- LD1
syn
) + KF2* (LD2
act
- LD2
syn
) +....
The overlay path is traversed as a speed offset with the incremental velocity (NC MD 300*) in
the case of following axes and with the M19 creep speed (NC MD 427*-434*) in the case of
following spindles.
With speeds/velocities which are lower than half the maximum value, the "Shortest path logic"
(maximum overlaid traverse path 0.5 revolutions) is traversed. In this case, half the maximum
velocity is the maximum permissible overlaid velocity.
In the case of speeds/velocities which are higher than half the maximum value, the overlay is
applied "in the slower velocity direction", i.e. overlay path in opposite direction to present
traversing direction, (maximum overlaid traverse path 1 revolution). In this case, half the
maximum velocity is the maximum permissible overlaid velocity.
The leading drives involved can also be simulated drives; in this case, the setpoint positions of
the leading drives are evaluated rather than the actual positions.
Leading drives which are not to be synchronized must be at standstill or decoupled.
Synchronization will not otherwise be successful. It will likewise not be possible to synchronize
the drives if the following drive is traversed simultaneously with overlay by the user or from the
program.
Depending on the setting of NC MD 1848*/526* bit 5 (Block change after synchronization
reached), block changes are disabled until the drives are fully synchronized.
Successful completion of the synchronization process is indicated by the interface signal
SYNCHRONIZATION REACHED.
The synchronization process can be aborted with RESET or LINK OFF; it remains, however,
active after RESET.
FEED DISABLE or override = 0 for the leading axis can abort synchronization. SPINDLE
DISABLE or override = 0 do not have any effect on the following axis.
12.18.9 Influencing the following error
Contour errors resulting from following errors can be reduced by means of the feedforward
control function (option).
The feedforward control permits a compensation component within the 0 % to 100 % range to
be specified via machine data. The feedforward control is effective for all setpoint inputs
(setpoints for actual/setpoint-linked leading drives, following drives, FD overlays) and can be
activated for leading and following drives (see Section "Functional description of feedforward
control" for further details).
12–140 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)