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Elliot Schwartz September 9, 1998 11:07

Extrusion Modeling
I have 2 questions about modeling extrusion processes:

(1) Does anyone have experience with modeling extrusion processes? I am wondering about the relative importance of viscosity vs. elasticity in modeling die swell in extrusion processes and the usefulness of various materials models.

(2) Does anyone have any experience with fluid flow analysis and/or inverse die design using POLYFLOW (from Fluent Inc.) or DIECALC (from Rapra Technology in England)? These are the 2 that I have found for extrusion modeling. If anyone knows of others, please let me know.

Thanks for any help.

Elliot Schwartz

Ivo Szarvasy September 11, 1998 19:08

Re: Extrusion Modeling
Die swell has two different reasons: a) a non-uniform velocity distribution at the die outlet and b) a non-relaxed stress field at the dies outlet. A non-uniform velocity field causes redrawing of the extrudate to finally end in a block stream. The stress field just redistributes due to changed boundary conditions. If one has a viscoelastic fluid one usually has to take a) and b) into account which implies calculation of velocity and stress field (both are dictated by the viscosity and elasticity law). I am using POLYFLOW in modelling PVC window profile extrusion. I am not aware of the type of problem you are thinking to use it for but from my experience it is not very well suited for complex and thin-wall profiles like ours. The problem usually becomes to highly non-linear and you get problems with POLYFLOWs numerical solution procedures. The next point is that, if you have to perform viscoelastic simulations, you are very fast at the limit of todays workstations (memory and CPU-time).

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