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Extrusion describes the process by which a polymer melt is pushed across a metal die, which continuously shapes the melt into the desired form. . . Gear pump. A Schematic of Profile Extrusion Line at FNAL . Introduction. Quality factors. Extrudate swell . Draw down . CoolingInsufficient mixing in the extruder Uneven die body temperatures and raw material variations Non-uniform viscosity in the dieNon-uniform swellingNon-uniform draw down.
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1. Extrusion Simulation and Optimization of Profile Die Design 03-25-2003
2. Extrusion describes the process by which a polymer melt is pushed across a metal die, which continuously shapes the melt into the desired form.
3. Quality factors
4. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
5. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
6. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
7. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
8. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
9. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
10. An attempt to develop a possible strategy for effective die design in profile extrusion
Investigate the die swell behavior of the polymer and to predict the optimum die profile-shape and dimensions, including the pin(s) profile, to obtain the required dimensions and quality of the extrudate.
Investigate the swell phenomenon and mass flow balance affected by different parameters like die lengths, flow rates, exponent in viscosity function etc.
Simulate the flow and heat transfer of molten polymer inside the die and in the free-flow region after the die exit, and compute pressure, temperature, velocity, stress and strain rate distributions over the entire simulation domain.
Investigate and understand over-all polymer extrusion process, and integrate the simulation results with the experimental data, to optimize the die design and ultimately to achieve better quality and dimensions of the extrudate.
Prepare the complete design of dies, including blue prints. Objectives
11. Design Methodology Using Finite Element based CFD code Polyflow?
Using the method of Inverse Extrusion
To fully understand the extrusion processes and the influence of various parameters on the quality of the final product.
Integrate the simulation results and the experimental data to obtain more precise extrudate shape.
12. Literature Review The text book “Dynamics of Polymeric Liquids” by R.B.Bird gives a detailed overview of non-Newtonian fluid dynamics, which is important to understand the flow of polymers.
The text book “Extrusion Dies” by Walter Michaeli gives an extensive representation of extrusion processes and guidelines for the design of dies.
The text book “Plastics Extrusion Technology Handbook” by Levis gives a clear representation of the rheology of materials and the technology of extrusion processes.
Woei-Shyong Lee and Sherry Hsueh-Yu Ho have investigated the die swell behavior of a polymer melt using finite element method and simulated flow of Newtonian fluid and designed a profile extrusion die with a geometry of a quarter ring profile
Louis G. Reifschneider has designed a coat hanger extrusion die using a parametric based three-dimensional polymer flow simulation algorithm, where the shape of the manifold and land are modified to minimize the velocity variation across the die exit.
W.A. Gifford has demonstrated through an actual example how the efficient use of 3-D CFD algorithms and automatic finite element mesh generators can be used to eliminate much of the “cut and try” from profile die design.
13. Governing Equations
15. Die Design The ‘art of die design’ is to predict ‘properly irregular’ die shape (with minimum number of trials) which will allow melt flow to reshape and solidify into desired (regular) extrudate profile.
The correct geometry of the die cannot be completely determined from engineering calculations.
Numerical methods
16. POLYFLOW? Finite-element CFD code
Predict three-dimensional free surfaces
Inverse extrusion capability
Strong non-linearities
Evolution procedure
19. Boundary Conditions
20. Boundary Conditions
21. Boundary Conditions
22. Boundary Conditions
23. Boundary Conditions
24. Boundary Conditions
25. Boundary Conditions
26. Material Data Zero shear rate viscosity, ?0 = 36,580 Pa-s
Infinite shear rate viscosity, ?8 = 0 Pa-s
Natural time, ? = 0.902
Transition Parameter, a = 0.585
Exponent, n = 0.267
Density, ? = 1040 Kg/m3
Specific Heat, cp = 1200 J/Kg-K
Thermal Conductivity, k = 0.12307 W/m-K
Coefficient of thermal expansion, ß = 0.5e-5 m/m-K
28. Profiles Rectangular profile die with one hole
Rectangular profile die with ten holes
29. Rectangular profile die with one hole
33. Simulation domain with boundary conditions
35. 19 hours and 36 minutes of CPU time Windows XP
2.52 GHz Processor
1 GB RAM
41. Exploded view of the extrusion die
43. Blue prints
44. Rectangular profile die with ten holes
51. One hour of CPU time Windows XP
2.52 GHz Processor
1 GB RAM
59. Blue prints
61. Conclusions The optimum dimensions of the die to attain more balanced flow at the exit were obtained.
The effect of inertia terms is found to be negligible for polymer flows at low Reynolds number.
The exponent of the Carreau-Yasuda model, or the slope of the viscosity vs shear rate curve, has a significant effect on the die swell.
The flow in the die appeared to be smooth with no re-circulation regions.
62. Recommendations for future improvements Polymer viscoelastic properties
Include flow, cooling, solidification and vacuuming in and after the calibrator
Radiation effects for free surface flow
Pulling force at the end of the free surface
Pressure of the compressed air
Non-uniform mesh
63. ACKNOWLEDGEMENTS Prof. Milivoje Kostic
Prof. Pradip Majumdar
Prof. M.J. Kim
Prof. Lou Reifschneider
NICADD (Northern Illinois Centre for Accelerator and Detector Development), NIU
Fermi National Accelerator Laboratory, Batavia, IL
64. QUESTIONS ?
