Siemens SINUMERIK 840D sl Function Manual page 148

Several Operator Panels on Several NCUs, Distributed Systems (B3)
Link axes
Position control
The position control is implemented on the NCU on which the axis is physically connected to
the drive. This NCU also contains the associated axis interface. The position setpoints for
link axes are generated on the active NCU and transferred via the NCU link.
Communication methods
There are two types of link communication:
● Cyclic communication
● Non-cyclic communication
Cyclic communication
● Setpoints for link axis
● Actual values of link axis
● Status signals of link axis
● Status signals of NCUs
are transferred cyclically. Actual values and status signals of a link axis are updated and
made available to the NCU that is interpolating this axis.
Non-cyclic communication
● Exchange of link variables
● Warm restart requirements
● Activation of axis container rotation
● Changes in NCU global machine and setting data
● Activation of axial machine data for link axes
● Alarms
Transfer time
Delays are incurred for transferring setpoints to the home NCU of a link axis and for
returning the actual values of this axis. With an interpolation group of local axes and link
axes, the control delays the setpoints for the local axes of the interpolating NCU by one
interpolation cycle, such that consistent values are taken into account for the interpolation.
If a channel needs the actual values of an axis of another NCU, e.g. a spindle with thread
cutting, two interpolation cycles will elapse before they are available. The setpoints then
generated are sent one interpolation cycle later to the position control for the above reason.
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Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions