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Basics of Web Tension Control Summary - TAPPI

Basics of Web Tension Control Summary Presenter: Darrell Whiteside, Sales Channel Manager Tension Control Maxcess International This presentation is intended to take the mystery out of web Tension Control . It is intended for operators, designers and engineers who would like a better understanding of their existing process and how they might improve both efficiency and consistency. The presentation covers the different aspects of machines including unwinds, rewinds and point-to-point applications. It also looks at the different methods of Control be it either speed or torque. Lastly we will explore the different types of Tension systems including: manual, open loop and closed loop. We will discuss different components and methods used in each, as well as the advantages and disadvantages. This section is intended to help the audience best select the system best suited to their individual applications.

Basics of Web Tension Control Summary Presenter: Darrell Whiteside, Sales Channel Manager – Tension Control Maxcess International This presentation is intended to take the mystery out of web tension control. It is intended for operators, designers and engineers who would like a …

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Transcription of Basics of Web Tension Control Summary - TAPPI

1 Basics of Web Tension Control Summary Presenter: Darrell Whiteside, Sales Channel Manager Tension Control Maxcess International This presentation is intended to take the mystery out of web Tension Control . It is intended for operators, designers and engineers who would like a better understanding of their existing process and how they might improve both efficiency and consistency. The presentation covers the different aspects of machines including unwinds, rewinds and point-to-point applications. It also looks at the different methods of Control be it either speed or torque. Lastly we will explore the different types of Tension systems including: manual, open loop and closed loop. We will discuss different components and methods used in each, as well as the advantages and disadvantages. This section is intended to help the audience best select the system best suited to their individual applications.

2 The audience should be able to take away some basic do s and don ts as well as some practical advice on how to improve their Tension . 2007 PLACE Conference September 16-20 St Louis, MOBasics of Web Tension ControlPresented by:Darrell WhitesideDistribution Channel ManagerMAGPOWRT erms and Relationships DefinedTorque = A force at a distance (X) that produces ortends to produce rotationForce = A push or pullXFORCETORQUE (TQ)= FORCE (F) x PERPENDICULAR DISTANCE (D)(from axis of rotation)Sometimes called "Lever Arm"FORCEXTENSIONTQ = T R TORQUE (TQ)= Tension (T) x RADIUS (R)Typical Tension Control ApplicationsNormal Running Conditions Unwind Rewind Point - to - PointTypical Applications - UnwindCenter UnwindBrakeTQ = T R T= TQR"Hold back" to create tensionTQ must decrease for constant tensionR is decreasingSurface UnwindBrakeT= TQRC onstantTQ must be constantfor constant tensionConstantCenter RewindClutchMotorT= TQR"Pull" web to create tensionTypical Applications - RewindR is increasingTQ must increase for constant tensionSurface RewindClutchMotorT= TQRTQ must be constant for constant tensionConstantConstantTypical Applications Point-to-PointNIPNIPD riveClutchMotorRTQ =TConstantNIPNIPD riveBrakeRTQ =TConstant torque produces constant tensionConstantCreating Tension ZonesWhat is a Tension zone?

3 A section of web where a different Tension can be created in the webBrake123 GearBoxMotor Nip points can differentiate Tension zones onlyifthe web cannot slip through themClutchMotorClutchT"S" WRAPTNIPTWhat are some typical sources used to create Tension zones?MotorWe show high ratio gear boxes or regenerative drives on the motorsSets Line SpeedMethods of Control (Speed Control )()1121212VV-VEAVVT=T+ RT1T2V1V2T2= Rewind tensionV2= Rewind velocityWhere:T1= Tension in the previous Tension zoneV1= Nip roll velocityE = Elasticity of the material A = Cross sectional area of the materialThe larger the elasticity (E), the less likely the material is to stretch. For most values of EA, useTORQUE CONTROLFor stretchy material, where E is small, speed Control canapproachbeing as good as torque controlSpeed Control CaseRT1T2V1V2()T=T VVEA V - VV2121211 += 10 lbIf we allow a error in V2:lb : error in speed results in error in : T1= 0V1= 100 fpmV2= 102 fpmEA = 500 lbControllingFunction= (102 fpm) V2= fpmThen:T2()fpm100fpm)100fpm102lb500fpm1 00fpm102lb0 + =() + =% Error =T2 Methods of Control (Torque Control )RTQ=T 2T1T2 Where:T2 = Rewind tensionR = RadiusTQ = TorqueTorque CaseMagnetic Particle Clutch or BrakeControllingFunctionT2= 10 lbAllow a error in torque (TQ):TQ= lb- error in torque results in a error in tensionTorque and Tension are directly related !

4 Example: R = 1 ftTQ = 10 lb-ftft1ft-lb10== 10 lb-ft ( )T1T2T=TQR2%25. Error == vs. Speed For a error in the controlled output, the resultant error in Tension was: = Magnetic particle clutch or other torque device = Speed caseExample: Driving a car with a fixed accelerator. Asyou go up a hill, the car will slow ControlOutputDesiredOutputControl(Amplif ier)TensionSystem(Machine)Output / Tension is influenced onlyby operator the operator walks away, the Control output does not changeTherefore, on unwind/rewind, Tension will change as the roll diameter changesManual SystemsExample: Driving a car and as you go up a hill, youtry to adjust the accelerator by visuallyestimating the incline. (No speedometer)Manual ControlOutputDesiredOutputControl(Amplif ier)TensionSystem(Machine)Output / Tension is influenced onlyby operator try to keep Tension constant as the rolldiameter changes, the operator must adjustthe Control output as he thinks it is SystemsExample: Driving a car equipped with a sensor that detects changes in incline and makes the accelerator adjustment to try to keep speed constant.

5 (Sensor is not measuring speed.)Open Loop ControlOutput / Tension is influenced byoperator adjustment and calculationsmade from a sensor (Machine)DesiredOutputOutputControl(Calc ulator)SensorOpen Loop SystemsExample: Driving a car and controlling the speed by adjusting the accelerator based upon the speedometer reading. (Actual speed feedback "Cruise Control ")TensionSystem(Machine)DesiredOu tputOutputControlComparatorLoad CellClosed Loop Systems Provide some form of feedback Tension Sensors Dancer Arm Free Loop Unwind ApplicationsHot brakes & web breaks. Rewind ApplicationsIf taper Tension is required. Point - to - PointConstant torque on a constant radiusequals constant Tension . Not good GoodYou get what you get,based on roll buildT=TQRC onstant7rpmTQ=SW T=TQRC onstant GoodT=TQRC onstantConstantConstantHP is constantManual Tension ControlsAutomatic Open Loop Tension Controls(Roll Diameter Compensation)Problem: Control needs some rotation tocalculate diameter.

6 On start-up, the Control does not know what output is ARMTC lutch or BrakeULTRASONICDEVICETORQUECONTROLRULTRA SONICSENSORC lutch or Brake Compensates for changes in roll diameter only Does not compensate for or reduce Tension transientsthat occur due to other parts of the systemOpen loop does not have Tension measurement Ultrasonic Control is the easiest to install and set upIt s easy and it works!Open Loop Systems Summary Does not compensate for Tension errors due to non-linearity ofdevice being controlled ( brake, clutch, motor feedbackClosed Loop SystemsFeedbackOutputControlTensionSyste m(Machine)SensorDesiredOutputComparatorT ENSION SENSOR SYSTEMTSBS ensor basedControlFeedbackDANCER SYSTEMBDFPD ancerControlDancerBRAKE Identify what is setting line speed Use a torque device to Control tensionSummary (do s and don ts) Make sure web does not slip through nips Don t use manual controls on center unwinds Beware of diameter calculator controls For indexing or out-of-round roll applications use a dancer system Don t Control Tension on the device setting line speedThank YouPRESENTED BYDarrell WhitesideDistribution Channel remember to turn in your evaluation)


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