Lenze EVS93xx CrossCutter - Manual (Page 37)

Cross Cutter
Features of the "Cross Cutter" prepared solution
 Prepared Solution Servo PLC / ECSxA 1.1 EN 2-23
Asynchronous cross cutter
"Asynchronous cross cutter" mode is a separate operating mode. It is frequently used when
very short material lengths need to be cut at a very high line speed. However, at the same time,
provision must also be made to ensure that the cut is made in asynchronism with the line
speed. In the prepared solution the maximum cutting length is limited to the cutting circle
circumference of the cross-cutter drum. This ensures that the cut is not made at an
undersynchronous speed at which the material to be cut would jam. This means that the
material is only ever cut at synchronous or oversynchronous speed. Unlike the scenario on the
synchronous cross cutter, the required cutting length is not modified by calculating a motion
profile. Instead, the master value is evaluated with an appropriate factor. The motion profile is
provided by a basic cam which runs through at a faster or slower rate in accordance with cutting
length (however, its speed will never drop below that of the line speed itself). This results in the
longest cutting length of the asynchronous cross cutter being equivalent to the cutting circle
circumference of the knife drum. The typical motion characteristics of an asynchronous cross
cutter are presented in Chapter 2.2.2. Since the line speed is adapted in "Asynchronous cross
cutter" mode and switching over to a different mode can cause a speed step change in the
master value, measures have been put in place to prevent direct switching to or from this mode.
You must stop the system first if you wish to switch from "Asynchronous cross cutter" mode to
"Continuous cutting", "Test operation" and "Reject operation". To change the cutting length in
asynchronous mode, you must first stop the cross cutter in order to avoid a speed step change.