Design Criteria in Numerical Design of Profile Extrusion Dies

Abstract:

Abstract. The rather unintuitive and non-linear behavior of plastics melts is a well-known obstacle in the design and manufacturing cycle of profile extrusion dies. This is reflected, for example, in the so-called running-in experiments, in which the already manufactured die is modified up to 15 times until the final product, shaped by the die, matches the quality requirements. Besides a homogeneous outflow velocity and thus homogeneous material distribution, an appropriate die swell is a second design objective which complicates the reworking of the manufactured die. We are conducting work to shorten the manual running-in process by the means of numerical shape optimization, making this process significantly less costly and more automatic. From a numerical point of view, the extrusion process is not as challenging as high-speed flows, since it can be described by steady Stokes equations without major loss of accuracy. The drawback, however, is the need for ac- curate modeling of the plastics behavior, which generally calls for shear-thinning or even viscoelastic models, as well as for 3D computations, leading to large computational grids. The intention of this paper is to investigate the application of specific geometry features in extrusion dies and their influence on objective functions in an optimization framework. However, representative objective functions concerning die swell and the incorporation of known geometry features, as used by experienced die designers, into the optimization framework still remain a challenge. Hence, the topics discussed are the influence of the mentioned geometry features on existing objective functions as well as an outlook on an algorithmic implementation into the optimization process with regard to representative objective functions.

• Periodical: Key Engineering Materials (Volumes 554-557)
• Pages: 794-800
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.554-557.794
• Online since: June 2013
• Authors: Roland Siegbert, Stefanie Elgeti, M. Behr, K. Kurth, C. Windeck, C. Hopmann
• Keywords: Extrusion, Finite Element Method (FEM), Objective Functions, Shape Optimization

References

[1] W. Michaeli Automatic optimization of extrusion dies, The Polymer Processing Society 23rd Annual Meeting, Bahia do Salvador, May 27-31, (2007)

[2] S. Elgeti, M. Probst, C. Windeck, M. Behr, W. Michaeli, and Ch. Hopmann Numerical Shape Optimization as an Approach to Extrusion Die Design, Finite Elements in Analysis and Design 61 (2012), pp.35-43

DOI: 10.1016/j.finel.2012.06.008

[3] M. Nicolai Shape Optimization for Fluids Using T-Splines as Shape Representation and Stabilized Finite Elements for the Fluid Flow Simulation, Ph.D. Thesis, RWTH Aachen University, (2012)

[4] M. Probst Robust Shape Optimization for Incompressible Flow of Shear-Thinning Fluids, Ph.D. Thesis, RWTH Aachen University, to be published in (2013)

[5] S. Elgeti Free-Surface Flows in Shape Optimization of Extrusion Dies, Ph.D. Thesis, RWTH Aachen University, (2011)

[6] P. J. Carreau and D. de Kee Review of Some Useful Rheological Equations, The Canadian Journal of Chemical Enginnering 57 (1979), pp.3-15

DOI: 10.1002/cjce.5450570102

[7] W. Michaeli, M. Behr, S. Elgeti, M. Nicolai, M. Probst, B. Fink, and C. Windeck Die Design: Automatically Optimizing Profile Dies, Kunststoffe International 7 (2009), pp.28-30

[8] M. Behr, S. Elgeti, M. Nicolai, M. Probst, W. Michaeli, B. Fink, and C. Windeck Towards Shape Optimization of Extrusion Dies Using Finite Elements, Journal of Plastics Technology (2009), pp.411-427

DOI: 10.1016/j.finel.2012.06.008

[9] A. A. Johnson and T. E. Tezduyar Mesh Update Strategies in Parallel Finite Element Computations of Flow Problems with Moving Boundaries and Interfaces, Computer Methods in Applied Mechanics and Engineering 119 (1994), pp.73-94

DOI: 10.1016/0045-7825(94)00077-8

[10] M. J. D. Powell The BOBYQA Algorithm for Bound Constrained Optimization Without Derivatives, Cambridge, England: Department of Applied Mathematics and Theoretical Physics, (2009)

[11] I. Szarvasy, J. Sienz, J. F. T. Pittman, and E. Hinton Computer Aided Optimisation of Profile Extrusion Dies: Definition and Assessment of the Objective Function, International Polymer Processing 15, no. 1 (2000), pp.28-39

DOI: 10.3139/217.1577