Nexen RSTC1100 964528 - Manual (Page 21)

21 FORM NO. L-21204-C-0705
SPLICING UNWIND APPLICATION
The RSTC utilizes “Smart Splicing,“ meaning that rolls of
different sizes can be loaded or spliced into the machine
without readjusting the controller. The RSTC will adapt
automatically to the new roll after receiving the splice signal.
When the splice input pulses high, the controller will reset
adaptation to the level defi ned by Splice Adaptation. This
shortens the time it takes for the RSTC to adapt its gains
to the new roll. The splice input can be used anytime a new
roll is loaded on the machine, with the machine running or
stopped. The splice input must be held high for at least
100 ms for the RSTC to detect this signal. The adaptation
process will begin immediately if the machine is running or
will begin after the RSTC receives a Run signal. NOTE: If the new roll is smaller than the one used to set
up Splice Adaptation, the adaptation level could start
out too high after a splice, and the tension may become
unstable until the gains have adapted down.
At the time of the splice, the RSTC must receive a Splice
A or Splice B signal. This will cause the corresponding
control output to become the active output controlling
web tension. If the new roll is to be controlled by Output B,
then the splice signal is given to the Splice B input. After
the splice signal is received, the opposite control output
goes into standby mode, causing the output to remain at
a constant level as specifi ed by STANDBY OUTPUT.
Small Roll Large Roll
Acceleration Acceleration
Run Speed Run Speed
Deceleration Deceleration
Stopped
Run/Stop Signal
Splice
Signal
Splicing Adaptation
Initial Adaptation
Optimum Gain
Reached
Adaptation
Figure 27
UNWIND APPLICATION
A typical unwind application begins with a new full roll. To
insure that the web tension reaches setpoint as quickly as
possible, the Splice signal can be used to reset Adaptation
to a higher level, set by SPLICE ADAPTATION, before
the machine starts. This shortens the time it takes for the
RSTC1000 to adapt its gains to the new roll.
If a Splice signal is not used, the web tension may take a
little longer to reach setpoint after the RSTC goes into the
Run mode. As long as this does not present a problem,
then the Splice signal can be ignored.
When the Run signal goes high at the Run/Stop input,
the RSTC will begin adapting from INITIAL ADAPTATION.
Adaptation is displayed graphically in the DIAGNOSTICS
window, however Adaptation and INITIAL ADAPTATION
values will not match, because INITIAL ADAPTATION is
one of several variables used to calculate Adaptation.
NOTE: The web must begin to move when the Run
signal is given.
As the roll begins to accelerate, the web tension will settle
on a level determined by TENSION SETPOINT. Next, as
the roll decreases in size, so will the Adaptation and Output
values. It is normal for the RSTC’s output value to fl uctuate
slightly as long as the web tension does not.
During a machine stop, Adaptation and Output values will
initially increase to overcome a roll’s inertia. After a Stop
signal is given, when the web has come to a stop, the
Adaptation value will reset to INITIAL ADAPTATION.
When the RSTC is in Stop mode, the Adaptation value
will remain constant and the Output value will change
depending on the web tension. The MAXIMUM OUTPUT
value is used to limit how high the output can rise. Likewise,
MINIMUM OUTPUT value is used to limit how low the
output can drop. This is useful for applications where a
minimal amount of output is necessary to over come the
spring force in a spring-disengaged brake.