Design Improvement of a U-Profile Extrusion Die Using Inverse CFD Simulation

1
Design Improvement of a U-Profile Extrusion Die
Using Inverse CFD Simulation
M. Kostic, Northern Illinois University Srinivasa
Rao Vaddiraju, Northern Illinois University Louis
G. Reifschneider, Illinois State University
2
Motivation and Objectives

• To design and fabricate a U-profile die for
  testing using a laboratory extruder
• To assess the role of CFD simulation for
  extrusion die design
• (1) die swell
• (2) mass flow balance, and
• (3) optimum die profile-shape
• How the simulation results compare to actual
  experimental results
• To assess the role of the calibrator in shaping
  the final profile of the extrudate
• Cooling simulation in the calibrator using the
  experimental data

3
Polyflow Inverse Extrusion SimulationGeneral
Assumptions
Body forces and Inertia effects are negligible
in comparison with viscous and pressure forces.
Specific heat at constant pressure, Cp,
andthermal conductivity, k, are assumed constant
4
Required Extrudate Profile
5
Viscosity Model Cross-WLF
HIPS DOW Styron 478 (MFI6) BASF 496N
(MFI2.8)
Pseudoplacticity included Viscoelastic effects
neglected.
6
Exploded View of Die Assembly
Melt Flow direction
Simulation determines Pre-Land Die Land plates
Pre-Land
Die Land
7
Finite Element Mesh

• MESH
• 16,592 hex. elem.
• 19,530 nodes.
• Solution
• Windows PC,
• 1 GB RAM,
• _at_ 2.39 GHz,
• Isothermal analysis required 552 minutes CPU.

8
Boundary Conditions (symmetry)
No slip at die surface
Inlet fully developed flow
Free Surface Zero traction No normal velocity
Symmetry Plane
Exit Zero normal stress Plug flow
9
Flow simulation only within the die
10
Representative Pressure and Velocity Results
11
Inverse Extrusion simulation results with
Pre-land and Die Land Contours
Extrudate Free Surface (Target Profile)
Symmetry Plane
(Target Profile)
12
Direct Extrusion simulation result with Styron
478 and Styron 496
478 direct extrusion extrudate profile
496 direct extrusion extrudate profile
Target extrudate profile
As expected the free surface outlet profile from
the results of direct extrusion with Styron 478
is very close to the target profile we used in
inverse extrusion CFD simulation.
13
Photograph of U-Profile Die Stack
14
Vacuum Calibrator Design
15
Schematic of U-Profile Extrusion Line with Data
Acquisition
Inlet IR
Upper T/C
Upper Exit IR
Upper Calibrator
Puller
U-Profile Die
Lower Calibrator
Puller
Lower Exit IR
Lower T/C
Product
16
Calibrator Set-up (opened)
Inlet IR
Exit Top IR
Die
Exit Bottom IR
Cooling Tank
17
Closed Calibrator
18
CalibratorExit Inlet
Die
Exit Bottom IR
19
Product Shrinkage at Calibrator Exit
20
Calibration rearranges mass balance
Air cushion mass balance
P_at_3 kg/hr (most uniform thickness) is 6 thinner
than target draw down and shrinkage affects.
21
HeatTransferData
Temperature data input to transient 1-D
simulation to iterate for effective heat transfer
between extrudate and calibrator.
22
Boundary Conditions for Extrudate Cooling
Simulation
23
Evolution of Temperature Contours as Extrudate
Passes Through Calibrator
24
Center-line Temperature History at Three
Critical Points
25
Conclusions

• Inverse extrusion simulation predicts profile die
  shape
• Custom tuning of profile dies still required.
• Total product design requires coupled design of
  the die and the calibrator, however
• Calibration design difficult due to coupled heat
  transfer and product deformation
• difficult to gather general empirical data,
• difficult to simulate due to contact element
  boundary conditions.

26
ACKNOWLEDGEMENTS

• Dr. M. Kostic and S. R. Vaddiraju thank
• NICADD (Northern Illinois Centre for Accelerator
  and Detector Development), NIU
• Fermi National Accelerator Laboratory, Batavia,
  IL
• NIUs College of Engineering and Department of
  Mechanical Engineering
• Dr. L. Reifschneider thanks
• College of Applied Science and Technology at
  Illinois State University for financial support
  to conduct the die design research.

27
QUESTIONS ?
28
Contact Information

• mailto kostic_at_niu.edu
• www.kostic.niu.edu
• mailto vaddirajs_at_yahoo.com
• www.vaddiraju.com

mailto lgreifs_at_ilstu.edu