CAE | process simulation
compounding process
Modeling the
Computer simulation of plastics processing offers an invaluable tool to experiment with multiple equipment designs and processing conditions without expending the time - and cost - of physically running an experi- ment on laboratory or large-scale equipment. Com- pounding industry professionals are likely to be familiar with simulation of injection moulding processes and even single-screw extrusion—these are relatively easy to simulate compared to the complex material flows and heat transfers found in twin-screw extrusion. However, simulation software for twin-screw extrusion does exist, with the first offerings appearing as long ago as the 1990’s. And while twin-screw compounding simulation has not yet become widespread, increases in computing power and advances in process understand- ing are certainly leading to better models that can provide real advantages for those ready to use them. In simulating the twin-screw compounding process,
a combination of one-dimensional (1D) simulation and three-dimensional (3D) simulations can be used. 3D-modelling uses finite element analysis (finite element method or FEM) for computational fluid dynamics (CFD) modelling, which is accurate and detailed for a localised point in the extruder. “3D CFD simulations are getting faster with the
increasing calculation power of computers so these simulations are becoming less time consuming and can be used for larger parts of the screw,” says Markus
www.compoundingworld.com
Computer-based simulation is not yet widely used in the compounding sector but, as software and computing power improves and
understanding of the benefits grows, its time may now have come. Jennifer Markarian reports
Schmudde, Manager Process Technology, Polyolefins, at Coperion in Germany. “In the past, 3D simulations were only used for fully filled screw elements. Today we can also simulate partially filled elements or mixing mechanisms with fillers (two-phase or three-phase simulation). But we are still far away from simulating a whole screw with a 3D simulation model.” The data gained from 3D methods can be used as a
basis for 1D simulation tools. This uses a simpler method and approximations to provide a broader view of the compounding process. Although 1D-simulation programs were originally developed many years ago, work to make the simulations more accurate is ongoing. Modules for reactive processing and devolatili- sation have been developed as “add-ons” for simulation programs. The University of Paderborn’s KTP Plastics Technology Institute in Germany, for example, along with a consortium of companies, aims to continually
Main image: Shorter
production runs and the
need for faster process
optimisation could see
compounders make greater use of available simulation tools
March 2017 | COMPOUNDING WORLD 15
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