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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