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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


at


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


ate


perceivedtensiontolerance (abi


ab


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


bilityfor themat ab


nt


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


ENSURING Ty


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


Tq/R


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


es in the ENSURING ACCURACY


but a few. CUR


/or lim ations , w.


itat


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.


SYSTEM MAINTENANCE IS KEY fe


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


fferent


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 .


NE NEW TECHNOLOGY TECHNOLOGY


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


fo


(TSC) provides a pr Torque Sensing Co


ecise, reliable ntrol System


nt web tension ntrolandtorqu


eb


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


To


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 .


AMULT MULTI-USE SYSTEM LTI-USE 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


fo


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


eatures patent pending technology. www.montalvo.o.com


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


w.


32


September 2016


www.convertermag.co.uk


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