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Web Maint O overal av

canbe ve tensionfo

We Te

ebTension&Guiding ng

Maintaining c nsisten open-lo optensioncont

ntaining consistent

pen-looptension controls tendtobe

providing constantunw ve for

ffective we canmostlyag

simple, inexpensive and veryeffe

ve nwind

foryourprocess.While agree that aat

closed-looptensioncontrol systemprovides themost accurat


webtensioncontrol, theremay beothermitigating factors that fav

ate andconsistent formof ay at

avour anopen-looptypeof systemfor aparticularprocess. Someof these factors include: all cost andcomplexityof

installing a closed-loopsystem, limitedmachine real estat availab


perceivedtensiontolerance (abi


process towithstandsignificant variabilityaroundtheoptimum ‘setpoint’ tension),orprocess restrictions and/o tonamebu

bilityfor themat ab


Typical open-loop tension control systems rely 100 per cent on roll diameter (indirect) fefeedback to control tension. Products such as ultrasonic sensors, lasers or proximity sensors are used to


roll’s diameter and relay this measure or calculate chang

infoformation to the tension

controller. The controllermonitors and/or calculates the roll diameter as it changes during the unwinding process, and automatically reduces

proportionally. As the T=Tq the torque of the brake


foformula dictates (see figur e 1), thi s willmaintain constant web tension fromfull roll to core.

There is no direct web fefeedback in order to actuallymonitor regulate control (hence the open loop control); due to t accuracy of the control system depends on the accuracy of the

Figigure 1 Fi

his, the term and


but a few. CUR

/or lim ations , w.


able for suchinstallations, aterialor

diameter calculation and the linearity of the torque device attached to the roll ofmaterial. To

feedback, another highly dependent quality fa

fe factor of an Torque devices include brakes,

motors, or drives that should deliver linear and responsive torque. Montalvo’s highly responsive and linear brakes deliver smooth, reliable torque throughout the entir e production run.

SYSTEMMAINTENANCE IS KEY In a well-maintained system, with a very linear torque device, open-loop tension control can provide tension accuracy within about 10 per cent of desired setpoint.We refer to this as the tension tolerance of your material and/or process. If the systemdegradesmechanically, or the linearity of the torque device is sub-standard or changes over time, this tension accuracy will be compromised.


If yourmaterials or process can withstand this level of tension variability, an open loop tension

option. It is certainly be control systemmay be

tter than a good

utilising amanual control system, which relies on the operators to make regular and consistent

changes to the torque level of the brake as the roll diameter changes (see figure 2).

As tension is being controller proportionally with no direct web

open-loop systemis the skill and experience of the operator to

ensure that the starting web tension (controller TRIMlevel/Starting Brake Output level) is cor material and proce

ss. If you run a rect fofor the

variety ofmaterials, and/or have several shiftfts and have diffe


operators, it can be challenging to obtain the same results consistently. In order to have a quality open loop tension control systemyou must have a high quality diameter calculation device, a linear,r, smooth torque device, an experience d operator, and a quality controller that can bring eve rything together .


However,r, newopen loop tension control technology has improved tension tolerances to approximately five per cent, (currently open loop tolerances are around 10 per cent compared to closed loop one or two per cent)whilemaking it easier for operators and adding quality and perfoformance to open loop processes. For the first time ever in an open loop control system,Montalvo’s To


(TSC) provides a pr Torque Sensing Co

ecise, reliable ntrol System

nt web tension ntrolandtorqu


ebtensio nwiit rq

fe t h que sensin g

tension reference that operators can use to ensure high quality, consistent production runs. The TSC systemadds the To

company’s newTorque Sensor (TS) to its V Series and CS Series brakes to provide an accurate, calibrated measurement of the torque being delivered by the brake at any given time (see the image below). Since we now know the brake torque (via the TS) and we know the roll radius, we now know exactly what the web tension is. Operators can now easily and consistently set and monitor the actual web tension fromstart to finish.

tension contro fofor the first tim


Combined with the responsive, linear torque delivery ofMontalvo Brakes; tension verification, availabl e e ever in open-loop l systems via the TS

Torque Sensor, creates a highly precise, consistent, and high perfoformance system .


Other systemadvantages include that the systemcan be utilised on here it is impractical

to install a typi applications w

systemdue to

space restrictions, cal closed loop

technical complexity, or cost

considerations. It also allows for an accurate tension refeference on systems where it would be


impossible to fit traditional load cells, such as onmachines where the web enters the process directly fromthe unwind.

eatures patent pending technology. 

The TSC is a total tension control solution that delivers perfoformance, convenience, and productivity. Simple, compact and easy to instal l and operate, it is the latest in open- loop tension control. The TSC ffe



September 2016

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