Self-Regulating Melt Valves for Polymer Processing

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Self-RegulatingMelt Valves forPolymer Processing

• David Kazmer
• May 12, 2005
• National Plastics Center

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Agenda

• Introduction
• Vision
• Design
• Validation
• Steady State Behavior
• Consistency
• Flexibility
• Clamp Tonnage Reduction
• Current Status

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Conventional Molding
Uneven processing inconventional molding
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Vision forInjection Molding

• Decouple the mold from the molding machine
• To increase supply chain productivity
• Decouple the gates from each other
• To increase part design flexibility
• To increase manufacturing flexibility
• To increase molded part consistency
• Decouple filling from the packing
• Increased molded part quality

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EnablerSelf-Regulating Valves
Complete process control for each gate
without pressure transducersor closed loop
controllers
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Valve Design

• Self-regulating valve
• Two significant forces
• Top control force
• Bottom pressure force
• Forces must balance
• Pin moves to equilibrium position
• Melt pressure is proportional to control force
• Intensification factor related to valve design

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Valve Function

• No sensor or controller needed!
• Valve adjusts to reject input variation
• Outlet pressure proportional to control force
• Pin position determined by inlet pressure and
  required pressure drop

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Valve Deployment

• Advantages
• Multi-axis melt control without cavity pressure
  transducers!
• Compact with low actuation forces
• Disadvantages
• Hot runner required

Provides flexibility,consistency,
andproductivity
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Performance AnalysisFlow Vectors
Annular flow provideslow shear rates pressures
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Performance AnalysisEffect of Position
Pin will hover near 1mmwith very fast response.
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Performance AnalysisEffect of Size
Higher melt flow withslightly larger valves
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Performance AnalysisOpen Loop Error
Open loop error 10NCorrectable error of 1-2
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Agenda

• Introduction
• Vision
• Design
• Validation
• Steady State Behavior
• Consistency
• Flexibility
• Clamp Tonnage Reduction
• Conclusions

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Validation

• All validation performed with a two cavity hot
  runner mold
• Mold Masters Lts (Georgetown, Ontario)
• Mold produced binder separators
• 1.8 mm thick by 300 mm long
• 10 g weight
• Three control schemes investigated
• Convention molding
• Open loop control
• Closed loop control with pressure feedback

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Air Pressure vs.Melt Pressure
Melt pressureproportional toair pressure
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Melt Pressure vs.Part Weight
Part weights adjustedwith air pressure
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Consistency StudyDesign of Experiments
Most significantparametersinvestigated
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Process Sensitivities
Machine sensitivitygreatly reduced
Intra-run variation (whiskers)greatly reduced
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Short and Long RunConsistency
Short and long runconsistencygreatly increased
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Quality Distributions
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Flexibility Example

• Use mold inserts to make differentcavities
• Use pressurevalve to controlweights size

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Control Actions
The valve settings wereoptimized within 30
minutes,no retooling
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Small Cavity Part Weights
Small parts acceptable bythird trial, optimal in
sixth trial
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Large CavityPart Weights
Large parts acceptable insecond trial,
optimalin sixth trial
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Pressure ProfilePhasing

• The processing of each cavity may be slightly
  offset in time
• By offsetting pressures, the moment of maximum
  clamp force is offset
• Slight extensions in cycle time can yield drastic
  reductions in clamp tonnage

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Pressure ProfilePhasing
Black curve offset fromgreen curve by 2 seconds.
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Clamp Tonnage vs.Cycle Time
10 increase in cycletime allows 50
reductionin machine tonnage!
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Current Status

• Intellectual property
• UML has filed a utility application
• Licenses under consideration
• Technology
• Being validated for extrusion
• Extrusion of multi-layer nano-composites
• New designs under development
• Valve gating
• Multiple materials