Nexen TC920V 964356 - Manual (Page 32)

29 FORM NO. L21268-C-1013
8. UNIT OPERATION
8.1 UNWIND APPLICATION
A typical unwinding application begins with a full roll. Prior to the Auto Trigger contact while the unit is in standby, the
START indicator is lit, and the control output is set at the Start Level. The Start Level should be set high enough such
that the full roll will not rotate freely when the machine is stopped, but low enough that the roll will begin to unwind while
the machine begins to accelerate during the start phase. During the start phase, the control output will typically be lower
than the control level during the automatic phase to mitigate against a web break as the roll inertia accelerates. After the
expiration of the Start Timer, the AUTO lamp will be lit and the control output is under automatic control and the tension
should stabilize at the tension set point.
During the stop phase, the Stop Level multiplier is set high enough to prevent the unwind roll from causing bagging in the
web while the roll inertia decelerates with the machine, but low enough as to not cause a weak break. During the stop
phase, the measured tension can be higher than the tension set point, depending on the Stop Level. The STOP lamp will
be lit during the stop phase, after which the START lamp will light-up indicating the unit is in standby and the set Start
Level is applied to the control output.
FIGURE 8.1 Typical Unwind Operation
Start Auto Stop Start Auto Stop Start
Auto Trigger
Front Panel
Indicator
T
2
T
2
T
1
T
1
Contr
ol Output / T
ension L
evel
Control Output
Tension Level
T
1
: Start Time
T
2
: Stop Time