Cleveland Motion Controls WebPro Unwind Brake Tension Controller MWP – 12662 - 0 REV BA - Manual (Page 4)

AO-70173
4
Revision BA
WebPro Unwind Brake Tension Controller
General Description
The WebPro Digital Tension Controller is part of a closed loop tension control system with transducer
feedback. The Controller continuously controls the web tension to the TENSION SET POINT value and
displays the true web tension on an LCD screen, either as a percentage or in engineering units. The
screen will display the tension applied to each transducer separately by pressing the < LEFT tension or
> RIGHT tension key. The sum of the LEFT and RIGHT tensions is displayed when the < > TOTAL key is
pressed. The Controller will control to the TOTAL tension value even when the LEFT or RIGHT tension is
being displayed. The Controller also has a dual range tension indication feature.
The measurement of actual web tension is made by sensing, with strain gauge transducers (sometimes
referred to as "load cells"), the force on a sensing roller caused by the tension in the web. The electrical
signal from the transducers is a combination of tension force and sensing roller weight. The weight of the
sensing roller is zeroed out electrically, leaving the tension force only to be displayed on the screen.
For wide web applications two transducers are recommended, one on each end of the sensing roller; for
narrow web, wire, cable and filaments one transducer can usually be used.
Unwind Brake System
The Controller may be used with an Electro-
pneumatic converter for pneumatic brakes
or a High Current Driver for electric brakes.
The torque of a center coupled unwind
brake must be reduced as the reel diameter
reduces in order to maintain constant
tension. It is the tension force alone which
pulls the web from the reel and overcomes
the unwind reel inertia on start up from rest
and during acceleration. The residual drag
torque of the brake added to any losses in
the machine will result in a minimum
operating tension. When the LOW tension
range is selected the Controller LOW output
may be used to disconnect pads from a
multipad brake for optimum performance.
Motor Powered Unwind System
Motor powered unwind systems can operate at tension levels lower than those of a brake system and can
generate tension when the machine is at rest (stall tension) provided the machine is designed to allow
this. The motor and drive must be suitable for continuous regenerative operation. The Controller requires
either tachogenerators ( tachos ) or encoders or a combination of both, for the unwind reel speed and for
the line speed. These speed signals are used by the Controller to calculate the reel diameter.
The Unwind Brake Controller has the software loaded for motor powered unwind control. If the Controller
is to be used for these applications contact CMC Inc for the AO-70172 handbook for these systems.
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