Siemens S7-300 Operating Instructions Manual page 16

Cam control basics
3.1 Properties of the cam types
Direction detection
The direction of the axis motion is determined as follows:
● At each pulse of the incremental encoder.
● With each error-free frame of an SSI encoder.
16
Enabling The cam is activated:
at the cam start, if the axis is

moving in positive direction and
positive effective direction is set.
at the cam end, if the axis is

moving in negative direction and
negative effective direction is set.
when the actual value lies within

the cam range.
Deactivating The cam is deactivated if:
the assigned distance has been

traveled
axis motion in reversed effective

direction is detected, and
hysteresis is not assigned
axis motion in reversed effective

direction is detected, and the
hysteresis is exited
the actual value no longer lies

within the cam range, e.g., "Set
actual value"/"Set actual value on-
the-fly".
Path length The path length of the cam is defined
by the cam start and cam end.
The cam start and cam end belong to
the active section of the cam.
On period The on period of the cam is determined
by the speed at which the axis travels
across the path length of the cam.
Position-based cam Time-based cam
The cam is activated:
at the cam start, if the axis is

moving in positive direction, and a
positive effective direction is set.
at the cam start, if the axis is

moving in negative direction, and a
negative effective direction is set.
After it has been activated, the full cam
activation time elapses, even if the
direction of motion of the axis changes
after the cam is activated. The cam is
not retriggered if its start position is
passed once again within the cam
activation time.
The cam is deactivated on expiration of
the assigned time, i.e., the activation
time is not restarted.
The path length of the cam is
determined by the axis velocity within
the cam activation time.
The on period of the cam is assigned
with the activation time.
FM 352 electronic cam controller
Operating Instructions, 05/2011, A5E01071724-03