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2008 International ANSYS Conference
Plastic Injection Molding Using ANSYS
Sarah Luo Ph.D.Senior. Mechanical Engineer Aurora Optical Inc.
Daniel RobinsonSenior Consulting EngineerPADT Inc.
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OUTLINE
• Introduction• Issue• Assumption• Approach• Simulation Results• Conclusions and Future Work
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Aurora Optical Inc. Introduction “A Quality Picture Worth
a Thousand Words”AO produces a wide range of camera modules, including FPC or socket based, Ultrathin, Macro, and Auto-Focus - custom module design is our business!
Camera Module Applications:• Personal Security Systems • Embedded PC Cameras • Mobile Phones • VoIP Phone Systems • Wireless Devices • Consumer Electronics • Medical Applications • Automotive Optical Systems
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PADT Intro -“We Bring Dimension to Your Ideas”
• PADT is an Engineering Services Company– Mechanical Engineering
• Design• Simulation• Manufacturing
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Issue:
A plastic part has larger shrinkage rate than steel parts during manufacturing. This is a major issue for our precision plastic parts.
An example of a plastic part with shrinkage over 7~10 µm during cooling
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Factors
Plastic Part Shrinkage varies depending on:
• Geometries• Material Properties• Process Parameters
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Advantages
Plastic injection molding process simulation provides:
• Shrinkage prediction for tooling compensations to produce parts with best precision
• Information for optimization, which can produce parts with minimum shrinkage and shortest cycle time
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Simulation Modeling
The simulation models a completed plastic injection molding cycle:
Inje
ctio
n
Eje
ctio
n
Gat
e Fr
eeze
-off
Packing and Holding
T(˚C
)/ P
(MPa
)
Mold Cooling
t (s)
Air Cooling
Clo
sing
Mol
d
Gate Temperature (Given)
Packing and Holding
Packing Pressure (Given)
Part TemperaturePart Pressure
Temperature/ pressure vs. Time during a cycle
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Approach
Workbench
CFX
Multiphysics
Static Analysis
3D Model
Shrinkage Profile
•Resin Material Properties•Plastic Injection MoldingProcess Parameters
• Solid Material Properties• Boundary Conditions
Thermal Transient Analysis
Plastic Injection Molding Simulation
CFX-Mesh
T (x,y,z,t)CFX Convection Load T(x,y,z,t)
Delta x, y, z
Mesh
P (x,y,z,t)Volume Fraction (t)
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Assumptions
• Polymers:1. Amorphous 2. Non-fiber reinforced
• Known Input:1. Process parameters 2. Gate temperature vs. time measurement data3. Material properties
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PVT Diagram for Amorphous Polymer Modeling
Five stages at PVT diagram:
• Injection phase: A-B
• Packing/Holding phase: B-C
• Gate Freeze-off and in-mold cooling phase: C-D
• Ejection parts: D
• Outside mold cooling phase: D-E
Polycarbonate
A
100 MPa
CDE
3002001000
Temperature (˚C)
Spec
ific
Volu
me
(cm
3 /g)
0.8
0.95
1
0.9
0.85
400
Tg
Tg
0 MPa
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Injection Phase
CFX Simulation Results:
• Injection flow
• Temperature
• Pressure
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Packing/Holding Phase
CFX Simulation Results:
• Volume Fraction
• Temperature
• Pressure
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Gate Freeze Phase
• Temperature
• Pressure
CFX Simulation Results:
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Transient Results of the In-mold (Cured) Cycle
• Transient Temperatureat the part center
• Transient Pressure at the part center
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Cooling after Ejection
Thermal transient analysis shrinkage results
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Shrinkage Data in Multiphysics
The shrinkage data are exported to Excel for shrinkage contour plots
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ANSYS results vs. Measurement Results
Shrinkage Predicted by ANSYS Measured Shrinkage*
* The data were provided by Process Engineer Rick Culler
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An Example of a Finished part using ANSYS Shrinkage Compensation
* The data were provided by Process Engineer Rick Culler
Measurement data after tooling compensation predicted by ANSYS*
Dimension Deviationactual-nonimal < 1µm !
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Process Optimization
• ANSYS Design Explorer Six-Sigma tools
• Design of Experiments performed to optimize mold temperature, deformation, stress
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Design for Six-Sigma
Input Parameters- Inlet temperature- Mold wall convective film coefficient
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Six-Sigma Analysis - Distributions
Output Parameters- Temperature- Directional deformation- Von Mises Stress
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Design Points – 3X3 DOE
Parameters varied –block factorial design, in order to characterize the design space
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Response Charts – Design Space
Response Parameters- Maximum deformation- Maximum Von Mises stress
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Min/ Max Values – Output Parameters
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DFSS Study – Summary
• Parameters varied were mold inlet temperature, mold to Lexan convective film coefficient for cooling
• Design of Experiments performed to examine effect of these parameters on cooled solid part deformation, maximum stress.
• Results show for inlet temperature = 240F (design point) hf = 5.895 Btu/hr-ft2-Fmaximum residual stress = 61.6 psi
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Conclusions and Future Work
• ANSYS results provide accurate shrinkage compensationfor tooling.
• Future work includes non-amorphous, fiber-reinforced polymer injection molding simulation, gate/runner optimization etc.
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Acknowledgements
• A special thank to Arnie Sen, Raymond Hsiao, George Kelly, and Dave Fredley for their consistent support of the project. Also thanks Rick Culler for providing shrinkage measurement data.
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Questions and Answers
Thank you!