1. ANTEC 2004 www.kostic.niu.edu/extrusion EXTRUSION SIMULATION AND EXPERIMENTAL VALIDATION TO OPTIMIZE PRECISION DIE DESIGN by Srinivasa Rao Vaddiraju, M. Kostic L. Reifschneider, A. Pla-Dalmau, V. Rykalin, A. Bross

2. ANTEC 2004 www.kostic.niu.edu/extrusion Introduction Twin-screw extrusion line Fermi National Accelerator Laboratory (FNAL) Northern Illinois Center for Accelerator and Detector Development (NICADD) Department of Mechanical Engineering Cast plastic scintillator - $40/kg Extruded plastic scintillator - $10/kg

3. ANTEC 2004 www.kostic.niu.edu/extrusion Berstorff 40-mm diameter, 1.36 m long, twin-screw extruder Two K-Tron automated feeders Conair downstream equipment Novatec compressed-nitrogen drier Profile Extrusion Line at FNAL Gear pump Cooling Dryer Cutter Feeding Hopper Extruder Die Calibrator Measurement Haul-off Polymer pellets Dopants Breaker plate

4. ANTEC 2004 www.kostic.niu.edu/extrusion Required Extrudate profile 2.0 1.0 0.11 All dimensions are in cm Rectangular cross section of 1 cm  2 cm with a circular hole of 1.1 mm diameter at its center, to accommodate wavelength- shifting optical fiber.

5. ANTEC 2004 www.kostic.niu.edu/extrusion Typical extrudate sample profile

6. ANTEC 2004 www.kostic.niu.edu/extrusion Effective die design strategy Die swell and optimum die profile-shape Flow and heat transfer Simulation Integrate the simulation results with the experimental data Objectives

7. ANTEC 2004 www.kostic.niu.edu/extrusion Polyflow  Finite-element CFD code Three-dimensional free surfaces Inverse extrusion capability Strong non-linearities Evolution procedure

8. ANTEC 2004 www.kostic.niu.edu/extrusion Flowchart for Numerical Simulation 1. Draw the geometry using a CAD software 2. Mesh the geometry 3. Specify Polymer properties and boundary conditions 6.Is the solution converged? Stop 4. Specify remeshing technique, solver method and evolution parameters Yes No 5. Solver solves the conservation equations using the specified data and boundary conditions Modify remeshing techniques, solver methods and/or evolution parameters Modify the mesh

9. ANTEC 2004 www.kostic.niu.edu/extrusion General Assumptions and incompressible Body forces and Inertia effects are negligible in comparison with viscous and pressure forces. The flow is steady Specific heat at constant pressure, C p, and thermal conductivity, k, are constant

10. ANTEC 2004 www.kostic.niu.edu/extrusion Material Data Styron 663, with Scintillator dopant additives Carreau-Yasuda Law for viscosity data: Measured by, Datapoint Labs, NY NOTE: Viscoelastic properties were neglected in our simulation

11. ANTEC 2004 www.kostic.niu.edu/extrusion Styron viscosity data, with and without Scintillator dopants 200 0 C 180 0 C 220 0 C η – Styron 663 η d – Doped Styron 663 10 6 10 5 10 4 10 3 10 2 10 -2 10 -1 10 0 10 1 10 2 10 3 Viscosity (Pa-s)

12. ANTEC 2004 www.kostic.niu.edu/extrusion Exploded view of the extrusion die

13. ANTEC 2004 www.kostic.niu.edu/extrusion Section 1 Section 2 Section 3 Die lip Melt flow direction Half domain of the extrusion die

14. ANTEC 2004 www.kostic.niu.edu/extrusion Simulation domain with boundary conditions 1. Inlet (Fully Developed Flow) 2. Wall (V n = 0, V s = 0) 3. Symmetry (V n = 0, F s = 0) 4. Free Surface (F s = 0, F n = 0, V.n = 0) 5. Outlet (F n = 0, V s = 0) 1

15. ANTEC 2004 www.kostic.niu.edu/extrusion Melt flow direction Die Lip 30,872 elements Skewness < 0.33 Finite element 3-D domain and die-lip mesh

16. ANTEC 2004 www.kostic.niu.edu/extrusion 19 hours and 36 minutes of CPU time Windows XP 2.52 GHz Processor 1 GB RAM Computation time Parametric Studies: preland and dieland, much faster

17. ANTEC 2004 www.kostic.niu.edu/extrusion Die lip Melt flow direction Contours of static pressure

18. ANTEC 2004 www.kostic.niu.edu/extrusion Die lip Melt flow direction Contours of velocity magnitude at different iso-surfaces

19. ANTEC 2004 www.kostic.niu.edu/extrusion Melt flow direction Die lip Contours of temperature distribution

20. ANTEC 2004 www.kostic.niu.edu/extrusion Contours of shear rate Melt flow direction Die lip

21. ANTEC 2004 www.kostic.niu.edu/extrusion Existing die, corresponding simulation and new improved-die profiles X (mm) Y (mm) New Die (Simulated) Existing Die Desired Extrudate Existing-Die Extrudate (Simulated)

22. ANTEC 2004 www.kostic.niu.edu/extrusion 2 D-View of the extrusion die Melt flow direction

23. ANTEC 2004 www.kostic.niu.edu/extrusion Conclusions Optimum dimensions of the die Effect of inertia terms – negligible Exponent of the Carreau-Yasuda model - significant effect Flow in the die: no re-circulation regions

24. ANTEC 2004 www.kostic.niu.edu/extrusion Recommendations for future improvements Include polymer viscoelastic properties Include cooling, solidification and thermo- mechanical stresses in and after the calibrator Radiation heat transfer for free surface flow Pulling force at the end of the free surface Nitrogen pressure inside the hole More non-uniform mesh

25. ANTEC 2004 www.kostic.niu.edu/extrusion NICADD (Northern Illinois Centre for Accelerator and Detector Development), NIU Fermi National Accelerator Laboratory, Batavia, IL NIU’s College of Engineering and Department of Mechanical Engineering Acknowledgements

26. ANTEC 2004 www.kostic.niu.edu/extrusion QUESTIONS ?

27. ANTEC 2004 www.kostic.niu.edu/extrusion Contact Information mailto: kostic@niu.edu kostic@niu.edu www.kostic.niu.edu mailto: vaddirajs@yahoo.com vaddirajs@yahoo.com www.vaddiraju.com Department of Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY