web tension control fundemenatals - aimcal...braking n t cw rotation driving n t driving ccw...
TRANSCRIPT
10/25/2018 1AIMCAL R2R Conference
Web Tension Control Fundamentals• Presented by:William Gilbert
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Improving Tension Control Performance
THEBASICS
Performance
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Web Tension Control
RewindUnwind Unwind
Process Process Section Isolation
Most converting machines have more than one tension zone. Each zone requires a control system and isolation from the neighboring zone(s).
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Unwinds
Center Driven Surface Driven Center / Turret
C C
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The Unwind
Tension is provided through a mechanical brake or a regenerative drive system.
The driven unwind is capable of a higher level of tension control performance.
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N
-T T
-N
NT
CW Rotation
Braking
NT
CW Rotation
Driving
NT
Driving
CCW Rotation
N
CCW Rotation
T
Braking
T =TorqueN = Speed
III
IVIII
The Unwind Section
Braking
A brake controlled unwind can only apply torque in the opposite direction of shaft rotation.
Braking
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N
-T T
-N
NT
CW Rotation
Braking
NT
CW Rotation
Driving
NT
Driving
CCW Rotation
N
CCW Rotation
T
Braking
T =TorqueN = Speed
III
IVIII
The Unwind Section
DrivingDriving
A driven unwind can operate in each of the four quadrants of rotational speed and torque.
BrakingBraking
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Advantages - Driven Unwind
Results: Wider tension ranges, larger build ratios and greater tension control accuracy.
Acceleration
Tension Disturbances
Performance
Appling torque in the direction of rotation
Response time & torque in the direction of rotation
Wider torque range, better torque regulation and faster torque response.
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Advantages - Driven Unwind
The combination of improved operation, reduced maintenance, power savings and energy conservation gives AC regen drives a clear advantage over mechanical brakes.
Energy Savings
Maintenance
Return Tension Energy to the line. (AFE ~ 1.0 PF)
AC motor
Advantage – Driven Unwind
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Zone Tension Control Challenges
Modern drive system systems can provide a high degree of performance, but they depend on the quality of the power transmission mechanics.
Poor mechanical characteristics, compliance and lost motion between load and motor, limit tension control performance
Power transmission components should be evaluated for mechanical stiffness including coupling, shafts, and core chucks / shafts.
Compliance & Lost Motion
Ks JLJM
TM
Motor Load
Power Transmission
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Zone Tension control – The Turret Unwind
The tension control system on turret unwinds and rewinds should take into consideration the velocity changes to the web as the turret indexes.
The addition (+/-) of web velocity should be included as a feed forward to the tension control system rather than letting the PID control determine and eliminate the error.
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Zone Tension controlConsideration should be given to selecting the lead section or master, typically the closest driven section to the unwind or the section that requires the highest level of speed regulation accuracy.
Sections should follow the web velocity or position setpoints rather than actual values.
Load Cell
OutfeedMarkReferenceSensorInfeed
Die Plate
Load Cell
Unwind Rewind
GEAR
PID
VMs
t
RG
ta t
v
Virtual Master
Speed Setpoint
GEAR GEAR GEAR GEAR PID
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Tension Control Modes
OPEN LOOP TENSION CONTROL
CLOSED LOOP TENSION CONTROL
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Open Loop Tension Control
Open Loop Torque Control
Speed controller
Current controller Converter
DRIVE
Setpoint
limits
Used when tension control accuracy is not critical
Cost considerations
Typical accuracy: >(+/-) 10%
Improved by: accurate inertia and friction compensation, use of synchronous motors
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Open Loop Tension Control
Used where the web has an acceptable and predictable modulus of elasticity.
Draw / Velocity Ratio Control
Speed controller
Current controller Converter
DRIVE
Setpoint
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Closed Loop Tension Control
Speed controller
Current controller Converter
DRIVE
Tension controller
Setpoint
Tension Feedback
Tension Sensor
Closed Loop Tension Control
Controlled tension via feedback device
Increased tension accuracy
Torque limiting or speed setpoint correction control
Loop Gain adaption, inertia compensation for large build ratios (Unwinds / Rewinds)
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Closed Loop Tension Control - Feedback Devices
Load Cells Dancer Roll System
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Dancer Roll Systems
A dancer roll system is a free moving idler, loaded with a force that is imparted to the web as tension as a result of the web positioning the dancer.
Tension Sensor≠
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Dancer Mechanical Configuration: Linear or Pivoting - (single wrap)
Linear Horizontal pivot Vertical top pivot Vertical bottom pivot
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Dancer Mechanical Configuration: Multi-wrap
Center Pivot RotaryMulti Wrap Pivoting
C
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Dancer Systems – Design Criteria
A change in web velocity without a change in dancer position will create a tension disturbance.
Low MassThe dancer is a position controlled device
Eliminate Friction Friction affects tension
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Dancer Systems – Sensing the Dancer Position
Traditionally a geared analog sensor or potentiometer.
High Resolution – 22 bit sin/cos (+4Mppr)
Absolute Position (single turn)
No gearing required
Zero Noise
Accurate starting diameter calculation
Optical Encoder (Sin/Cos)
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Dancer Systems – Loading the Dancer Arm
Rolling Diaphragm Pneumatic Cylinder
Rolling Diaphragm Cylinders provide a low friction conversion of pneumatic pressure to linear force.
Highly sensitive to force changes
No line lubrication required
Low friction - (circulating ball bearing)
No pneumatic leakage
Wide range of sizes
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Dancer Systems – Supplying the Cylinder pressure
Electro-Pneumatic Regulator
A change in dancer position will affect the pressure in pressure in a the cylinder
Requirement: High forward and reverse flow
Remote tension adjustment
Enables taper tension
Voltage or current commands
Output pressure ~ pseudo tension indication
*Courtesy of Proportion Air
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Dancer System Overview
Advantages
Disadvantages
+30.0°
-30.0°
Typically uses on Unwind / RewindNot a sensorPosition controlled via web length changeDancer force = Web TensionPivoting type the most common (+/- 30 degrees)
Storage / Absorb tension transientsStarting diameter calculation
Design critical for functionalityTension indicationTension range
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Accumulators
Accumulator position
INFEED OUTFEED
Accumulator axis
Tension control load cell
UNWIND
Variable speed section Constant speed section
vOUTvIN ACCUMULATOR UNIT
Used for storage when stopping a section (roll change / splice, etc.)Types: Loaded & DrivenDriven type - offers best tension control
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Tension Sensors – Load Cell Styles / Options
Dead Shaft
Cartridge Compact Pillow Block / Heavy Duty
Live Shaft Live Shaft
In Roll / Cantilevered
Cantilevered
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Tension Sensors – Strain Gauge Functionality
Load Cell Supply
Bridge Output (mv)
Tensio
n Tension
Compre
ssion
Compression
Load Cell Half #1
Load Cell Half #2
Tension
Compression
Tension
Compression
Tension Signal Output
Load Cell Excitation
WEB TENSION FORCE
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Load Cells – Connecting to the Controller
Traditionally used with analog amplifiers (mv in to 10vdc output).
Load Cells Load Cells
mV signal
Load Cell Amplifier
Tension control 0-10vdc analog
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Load Cells – Connecting to the Controller
Most load cell manufacturers produce amplifiers that support the popular industrial networks.
Load Cells Load Cells
mV signalLoad Cell Amplifier
PLC / Tension control
Industrial Ethernet Network
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Load Cells – Connecting to the Controller
Optimal Solution: Load Cell amplifier in a machine located remote I/O module
Load Cells Load Cells
mV signalLoad Cell Amplifier
PLC / Tension control
Industrial Ethernet Network
Measuring technology seamlessly integrated into the automation system
Remote I/O
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Tension Sensors - Strain Gauge Load Cell
Advantages
Disadvantages
Load Cell (Strain Gauge)AccuracyDirect MeasurementRanges: 15-20:1 Cartridge
50:1 CompactDual Load cell option to +200:1
Low voltage signal (mv) – requires amplificationNoise / may require filteringSubject to overloadCalibrationPotential temperature drift
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Tension Sensors - LVDT
Pivot Point Differential
Transformer LVDT
LVDT, (Linear Variable Displacement Transformer)
High Signal Level output
Pillow Block Style Mounting
Used for higher tension ranges
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Tension Control – Closed Loop control Options
TORQUE LIMITATION CONTROL
SPEED SETPOINT CONTROL
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Tension Control in the Winder – Closed Loop Torque Control
CURRENT CONTROLLER
CURRENT LIMIT
SPEED CONTROLLER
GAIN ADAPT
TAPER TENSION
DIAMETER CALC
D
0
1
WEB TRANSPORT
V CONSTANT
JOG
ACTUAL TENSION
INERTIA CALC
dn/dt FRICTION
JOVERSPEED
TENSION CONTROLLER
_
TENSION SET GAIN ADAPT
ACTUALTENSION
LOAD CELL
F
n+M+
MassDiameter & TensionFriction & Mech. LossesChanging Diameter
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Tension Control in the Winder – Speed Setpoint Correction
CURRENT CONTROLLER
CURRENT LIMIT
SPEED CONTROLLER
GAIN ADAPT
TAPER TENSION
D
WEB TRANSPORT
V CONSTANT
ACTUAL TENSION
INERTIA CALC
dn/dt
J
TENSION CONTROLLER
_
TENSION SET GAIN ADAPT
ACTUALTENSION
LOAD CELL
DIA. CALC
F
n+M+
MassDiameter & Tension
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Tension control – Mode Selection
OPEN LOOP TORQUE CONTROL(Indirect)
CLOSED LOOP TORQUE CONTROL(Direct)
SPEED SETPOINT CORRECTION
Three Tension Control Modes
The selection of the tension control mode can be influenced by several factors, including machine specifications or design, the type of tension sensor used.
A major the determining factor will be the compliance of the web.
The modes of torque control / limiting are commonly implemented when the web material has a very low compliance or is “non-extensible”, e.g. heavy paper, steel, aluminum, other metals or foils.
The mode of tension regulation via speed correction is ideally implemented when the web is compliant or “extensible”.
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Thanks for your attention!
* Contact us for a Converting Toolbox Flash Drive
William GilbertSiemens Industry, Inc.5300 Triangle ParkwayNorcross, GA 30092Mobile: +1 (678) 314-4222E-mail: [email protected]: www.usa.siemens.com/converting