Modeling and simulation for varying die gap fluid extrusion

TL;DR

This paper introduces two mathematical models to simulate the effects of varying die gap in fluid extrusion, using physics-based PDEs and a parameter identification scheme, to improve understanding and control of extrusion processes.

Contribution

It presents novel physics-based and data-driven models for simulating varying die gap extrusion, including a new numerical method for free surface definition.

Findings

Effects of die gap variation on extrudate shape analyzed

A new numerical method for free surface modeling proposed

Parameter identification scheme replicates physics-based model results

Abstract

The analysis and the simulation of fluid extruded out of a die opening are of great importance in different industrial applications. Mathematical modeling and experimental studies of extrusion out of a constant die gap has been the subject of numerous publications in the literature. Extrusion Blow Molding is a polymer forming technique used to manufacture a wide range of large hollow parts such as fuel tanks used in the automotive industry. The die gap is varied during extrusion to adjust the manufactured product's final thickness and to compensate for uneven stretching during molding. In this work, mathematical modeling of varying die gap extrusion is introduced. Two models using different approaches are presented to model the time dependent effects of varying the die gap on the extrudate. In the first approach, physics based partial differential equations are used to simulate extrusion. The Navier Stokes equations are used as governing equations to simulate molten polymers. The governing equations are solved using Arbitrary Lagrangian Eulerian based Finite Element Method. A novel numerical method for defining the free surface of the extrudate is proposed. In addition, the effects of varying the die gap on the material velocity, pressure and extrudate shape are reported. In the second approach, a parameter identification scheme is used to obtain the parameters of a novel model with a predefined structure. The purpose of the proposed model is to replicate time dependent extrudate thickness of the physics based model.