ANTEC 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

ANTEC 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

ANTEC 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

ANTEC Required Extrudate profile 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.

ANTEC Typical extrudate sample profile

ANTEC 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

ANTEC Polyflow  Finite-element CFD code Three-dimensional free surfaces Inverse extrusion capability Strong non-linearities Evolution procedure

ANTEC 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

ANTEC 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

ANTEC 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

ANTEC Styron viscosity data, with and without Scintillator dopants C C C η – Styron 663 η d – Doped Styron Viscosity (Pa-s)

ANTEC Exploded view of the extrusion die

ANTEC Section 1 Section 2 Section 3 Die lip Melt flow direction Half domain of the extrusion die

ANTEC 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

ANTEC Melt flow direction Die Lip 30,872 elements Skewness < 0.33 Finite element 3-D domain and die-lip mesh

ANTEC 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

ANTEC Die lip Melt flow direction Contours of static pressure

ANTEC Die lip Melt flow direction Contours of velocity magnitude at different iso-surfaces

ANTEC Melt flow direction Die lip Contours of temperature distribution

ANTEC Contours of shear rate Melt flow direction Die lip

ANTEC Existing die, corresponding simulation and new improved-die profiles X (mm) Y (mm) New Die (Simulated) Existing Die Desired Extrudate Existing-Die Extrudate (Simulated)

ANTEC D-View of the extrusion die Melt flow direction

ANTEC 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

ANTEC 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

ANTEC 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

ANTEC QUESTIONS ?

ANTEC Contact Information mailto: mailto: Department of Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY