twin-screw extrusion | Computer modelling


moves down different screw lengths. A process trends analysis compares multiple simula-


tions (into the hundreds, if necessary) to evaluate the affect of screw RPM on material viscosity and other machine operations on different material features. A design of experiment capability tests material or


process sensitivity under a range of operating condi- tions. It can also check the functioning domain of a material for specifi c screw confi gurations and operating parameters, such as screw speed, residence time, throughput, torque limit and other features. SCC’s Ximex mixing and extrusion simulation


software combines computational fl uid dynamics (CFD) with 3-D software to produce graphic analyses of material behaviour during compounding and related


processes such as continuous mixing, planetary mixing, kneaders, batch and static mixing. The analysis is “very graphic,” says Chassagnolle, and can be displayed as video or in 3D images. The software models material fl ow only through the mixing section of a twin-screw extruder to extract a CFD analysis and thermo-mechanical data based on the performance characteristics of the materials being compounded.


The objective, Chassagnolle explains, is to measure the mixing effi ciency of the process as confi gured and account for limitations on materials, especially heat-sensitive polymers and additives. One point of interest, for example, is the impact of accumulator heat generated by kneading blocks and mechanical heating on such materials.


The CFD analysis provides initial data on tempera- ture, pressure, viscosity and shear. The graphics then convert the compound into multiple particles, colour- coded according to the accumulation of process heat on them. In particle form, the compound is reportedly easier to follow and analyze during process simulations. The condition of the particles shows how effective distributive mixing is and compares mixing effi ciency to material limits. Real-time graphs monitoring particle elongation and other process conditions are displayed to augment data.


Ximex, which also benefi ts from CEMEF input, can be set up to simulate all screw confi gurations due to a mesh immersion feature that automatically transfers these geometries from CAD fi les.


The thermo-mechanical history of a compound is shown on SCC’s Ludovic 1-D software at various stages of extrusion


With compounders looking for ways to improve productivity, reduce development and operational expenses, and increase competitiveness, examining the options available in modelling and simulation software should be on their to-do list. The advances in this area of compound and process development provide an impressive technical and business tool for all types of operations, large, small, specialty and commodity.


Click on the links for more information:  www.centuryextrusion.com  www.polytech-soft.com


 www.polymers-ppi.com (Newark)  www.scconsultants.com  www.uni-paderborn.de/en/  www.uakron.edu/ipspe/ (Akron)  www.temarex.com  www.hasl.co.jp  www.ansys.com  www.brunel.ac.uk


Particle tracking is an SCC Ximex software function that enhances statistical analysis of mixing effi ciency


40 COMPOUNDING WORLD | February 2015  www.utb.cz (Tomas Bata)  www.cemef.mines-paristech.fr www.compoundingworld.com


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