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2005 CFD Summit The Meeting of the Minds in Flow Modeling June 7-9, 2005 Dearborn, Michigan. Design Improvement of a U-Profile Extrusion Die Using Inverse CFD Simulation. M. Kostic , Northern Illinois University Srinivasa Rao Vaddiraju , Northern Illinois University

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

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2005 CFD SummitThe Meeting of the Minds in Flow ModelingJune 7-9, 2005Dearborn, Michigan

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


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


The flow is steady

and incompressible

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


27.94 mm

25.4 mm

(2.54 mm thick)

Required Extrudate Profile


h

(

T

)

&

h

g

=

0

(

T

,

)

,

where

-

1

n

&

h

g

æ

ö

(

T

)

+

1

0

ç

÷

t

*

è

ø

é

ù

-

A

(

T

D

)

h

=

-

1

2

(

T

)

D

exp

ê

ú

0

1

+

-

A

(

T

D

)

ë

û

2

2

Viscosity Model: Cross-WLF

HIPS: DOW Styron 478 (MFI=6)

BASF 496N (MFI=2.8)

Pseudoplacticity included Viscoelastic effects neglected.


Extruder Die Mounting Plate

Extruder U-Profile Adapter Plate

Transition Plate

Exploded View of Die Assembly

Melt Flow direction

Simulation determines Pre-Land & Die Land plates

Pre-Land

Die Land


MESH

16,592 hex. elem.

19,530 nodes.

Solution

Windows PC,

1 GB RAM,

@ 2.39 GHz,

Isothermal analysis required 552 minutes CPU.

Finite Element Mesh


Pre-land inlet geometry fixed

Die land: uniform passage

Free surface exit matches target extrudate: fixed

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


Profile of the inlet to the pre-land plate was determined by a series of trial and error extrusion simulations to insure a balanced mass flow exiting the die.

Outlet 1

Outlet 2

Outlet 3

Outlet 4

Outlet 5

Outlet 7

Outlet 6

Flow simulation only within the die


Pressure (Pa)

Velocity Magnitude (m/s)

Representative Pressure and Velocity Results


Die Land

Pre-land Inlet

Pre-land Inlet

Die Land

Inverse Extrusion simulation results with Pre-land and Die Land Contours

Extrudate Free Surface (Target Profile)

Symmetry Plane

(Target Profile)


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.


Photograph of U-Profile Die Stack


Vacuum Lines

Extrudate Passage

Cooling Lines

Stacked Plate Design: Passage matches target profile, no taper along flow direction.

Vacuum Lines

Vacuum Calibrator Design


Cut Off

Cooling Tank

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


Calibrator Set-up (opened)

Inlet IR

Exit Top IR

Die

Exit Bottom IR

Cooling Tank


Closed Calibrator


CalibratorExitInlet

Die

Exit Bottom IR


Corner pulling away

Side wall shrinkage: 3% – 6%

Air gap = shrinkage

Product Shrinkage at Calibrator Exit


Calibrated mass balance

E

G

C

A

I

Calibration rearranges mass balance

Air cushion mass balance

[email protected] kg/hr (most uniform thickness) is 6% thinner than target: draw down and shrinkage affects.


Fredette

Order of magnitude difference: can testing results be generalized?

HeatTransferData

Temperature data input to transient 1-D simulation to iterate for effective heat transfer between extrudate and calibrator.


Boundary Conditions for Extrudate Cooling Simulation

Free Surface

L = 50 mm

+ h

h

= h

conv

tot

rad

Tinlet = 505 K

= 10 W/m2K + 15 W/m2K

T

= 295 K

Calibrator

L = 95

mm

2

= 303 K

h

= 175 W/m

K, T

upper

2

h

= 225 W/m

K, T

= 297 K

lower

h

upper

h

low

er

V = 6.3 mm/s

Adiabatic

Adiabatic


Evolution of Temperature Contours as Extrudate Passes Through Calibrator

150 - 200

  • Temperature History Plot Points

    • Upper

    • Middle

    • Lower

200+

150 - 200

100 - 150

100 - 150

50 - 100

Black area solidified

Inlet

Outline of full profile shown

Midway

< 50

Exit


Center-line Temperature History at Three Critical Points


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.


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

    • NIU’s 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.


QUESTIONS ?


Contact Information:

mailto: [email protected]

www.kostic.niu.edu

mailto: [email protected]

www.vaddiraju.com

mailto: [email protected]


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