Inverse shape design in injection molding based on the finite element method

  • Inverses Design in Spritzgussverfahren basierend auf der Finite-Elemente-Methode

Zwicke, Florian; Behr, Marek (Thesis advisor); Veroy-Grepl, Karen (Thesis advisor)

Aachen (2020)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2020

Abstract

A method is proposed for the inverse design of cavity shapes for the injection molding process. When liquid polymer melt is cooled down in an injection mold to manufacture plastics parts, inhomogeneities in the cooling and solidification processes lead to shape defects in the finished molding. The geometry of the cavity where the liquid melt is injected is largely responsible for the shape of the molding. The method described in this document offers an automatized tool for the determination of a suitable cavity shape that will reduce faults in the molding shape. The basis of this method is a numerical simulation of the injection molding process. This method builds on simulation models for both fluid and solid polymers that incorporate the important physical phenomena of thermoviscoelastic material behavior and solidification. Separate simulation models are described in this document for the solidification and post-ejection stages of the process. They are both equipped with a finite element formulation that makes them suitable for a swift implementation in a computer code. The inverse design method for the cavity shape results from a combination of an inverse formulation of stationary thermoelasticity with an iteration scheme that incorporates the non-elastic effects. This iterative method is demonstrated for two sample cases. The simulation method is shown to represent the important aspects of the viscoelastic behavior and solidification. The iterative inverse design method produces suitable cavity shapes after small numbers of iteration steps. Furthermore, plots of a distance measure over the course of the iteration indicate rapid convergence of the method.

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