8/11/2019 Understanding dancer tension control system.pdf
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Presented by: Darrell WhitesideDirector Sales-Tension Control
MAGPOWR
Understanding DancerTension Control Systems
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• Manual systems
» Closed loop
» Open loop
• Automatic systems
System Types
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F e e d b a
c k
Control adjusts brake torque up or down
B
Sensor measures tension
LC
Load Cell System
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DANCERCONTROL
BRAKE
SENSOR
POSITION
Typical dancer control systemDancer Systems
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Why Use Dancers?
Accumulation for Out-of-Round Rolls
Accumulation for Indexing Applications
Accumulation for Zero Speed Splicing
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DFP
How Dancers Work
1st Commandment
• The load on the dancer sets the tension!
2nd Commandment
• The load on the dancer must not change!
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+ MA + DV + KX
T T
L
M
X
2T = L
T = Web TensionL = Load Set by Loading
Device + Dancer Weight
M = Mass
A = Acceleration
D = Damping Factor
V = Velocity
K = Spring RateX = Deflection
Ideal Condition: 2T = LHow do we get there?
Forces (F) on a Dancer
00≈0
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Loading Dancers
LOAD
DFP
TC5
CGM
• 1 - Clutch and cable
Magnetic Particle
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1. Clutch and cable
Magnetic Particle
2. Pneumatic cylinder and regulator
Use a rolling diaphragm type cylinder •Bellafram
•Illinois Pneumatic
•Control Air
Quick relieving
DFP
Loading Dancers
Air In
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1 - Clutch and cableMagnetic Particle
2 - Pneumatic cylinder and regulator Use a rolling diaphragm type cylinder
3 – SpringsLoad changes as spring is stretched from rest position
4 - Weights (Counter balance)
They add mass5 - Shock absorbers
Load changes with velocity of dancer
DFP
Quick relieving
kg
Loading Dancers
Effect of Position Velocit &
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Dancer Arm:
• Should be long enough• Should be positioned far enough away from adjacent
idler rolls so the load on the dancer arm does not change
• Arcs of 30o- 90o are common
Loading Device should be:
• Independent of position
• Independent of velocity
• Independent of direction of motion
2TL ≠
Effect of Position, Velocity &
Direction
of Motion on Dancer
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DFP
Air Cylinder& Regulator
• Velocity affects air cylinder & regulator combination
• Pressure regulator can make or break dancer system
• Must have sensitive relieving regulator (grab dancer arm & pull up quickly)
AirReservoir
Recommended: Add an air reservoir between the regulator and cylinder. The
reservoir volume must be much larger than the cylinder volume
Air Cylinder Loading of
Dancer & Cautions
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Position Sensor
Assume 1° of Dancer rotation results in an
output/torque change of 5 (lb-ft)….”Gain” What happens to Tension?
RollFull@lb5(ft)1
ft-lb5 Δ
T ==
)(
Gain Affects on Dancer Position
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Gain Affects on Dancer Position
CORE
R = .25 FOOT
1 ROTATIONO
Assume 1° of Dancer rotation results in an
output/torque change of 5 (lb-ft)….”Gain” What happens to Tension?
Core@lb20(ft)0.25
ft-lb5 Δ
T ==
)(
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Summary of Gain
Affects on Dancer Position
Review Roll Dimensions
Full Roll Diameter of 1 (ft) Core Diameter of 0.25 (ft)
Tension Change Due to Roll Diameter Reduction
5 lb @ Full Roll
20 lb @ Core
} Roll Build
Ratio of 4:1
}Tension Changes by the Roll Build Ratio,
but Inertia(Unwind Gain) Changes by R3, or 1:64
Larger Roll Build Ratios are Common!
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Evolution of Gain(System Gain = Control Gain + Unwind Gain)
“The Past”
w/o Gain Compensation
F u l l R o l l
C o r e
Diameter
G a i n
System Gain w/o Compensation
Control Gain w/o CompensationUnwind Gain
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Methods to Minimize
Gain Affects
Reduce the Roll Build Ratio Impossible!!!!
Operate Dancer Control with Low Gain Slow Response (Sluggish)
Dancer May Hit Stops
Set Gain Proportionate to Roll Size Use a Gain Compensating Dancer Control
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Evolution of Gain(System Gain = Control Gain + Unwind Gain)
“ The Past”
w/o Gain Compensation
F u l l R o l l
C o r e
Diameter
G a i n
System Gain w/o Compensation
Control Gain w/o Compensation
Unwind Gain
“Today”
w/ Gain Compensation
Diameter
System Gain w/ Compensation Control Gain w/ Compensation
Unwind Gain
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Summary
Use Dancer Systems for Accumulation Out-of-Round Rolls
Indexing
Zero Speed Splicing
Use a Quality “Non-Stick” Rolling Diaphragm AirCylinder
Make the Arm as Light as possible No Springs, Dampers or Weights
For Large Roll Builds use a Gain Compensating
Control
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Thank you!
Darrell Whiteside
Director of Sales- Tension ControlMAGPOWR
www.magpowr.com
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