PROCESSING | SIMULATION
Right and below: Automated slicing allows flow in the extruder screw channels to be modelled in Sigma3D
IMAGES: KUNSTSTOFFTECHNIK PADERBORN
“This requires a high degree of experience to perform an appropriate evaluation. With these developments in Sigma, we want to give engineers a tool that simplifies the evaluation and speeds up the process of screw design. Using the current investigation on material degradation, an evalua- tion of the calculation possibilities of molecular weight degradation in the twin-screw process will be carried out. This will serve as a basis for further Sigma projects, which will consider calculation of molecular weight degradation.”
both the flow properties during processing and the mechanical
properties of the final product. With this in mind, KTP plans to investigate and analyse molecular weight degradation during the processing of polypropylene. Parameters considered for the investigation include shear rate, residence time and tempera- ture, all of which will be varied with different screw and temperature configurations, as well as speeds and throughputs. The intention is to develop the foundations for development of gentle processes, which will also take into account boundary condi- tions such as high throughput. The work will focus on PP because it is one of the most important industrial mass-consumption plastics. The investi- gation aims to assess material degradation through the intrinsic viscosity of different PP types that differ with regard to melt flow index. The Sigma3D interface allows a combination of solutions by numerical one-dimensional process simulation. KTP says that that following the success- ful introduction of the software, further work now has to be done on development of the Sigma3D module. This will involve the extension of evalua- tion options for the user. KTP says that twin-screw extruders are essen- tially defined by three different geometric zones - channel, intermeshing area, and gap. The first evaluation will obtain further knowledge about the process in relation to these zones for important factors such as flow velocity and shear rate. The second will consider the channel zone in detail. Helixes can be placed next to the front section on the x-axis of the screw elements (slices) in the channel, which will be able to determine conclu- sions about flow in the channel direction. One of the long-term goals at KTP is the development of automated process optimisation. “At the moment, evaluation of the designed screw is done by the process engineer,” says Malatyali.
40 COMPOUNDING WORLD | March 2021
Reliable results The most important requirements for any computer modelling software is the reliability of the model and consequently the accuracy of the results, according to SC-Consultants. The French company is the developer of both the XimeX-TSE and Ludovic software for twin screw process analysis. “The materials that we now need to consider are becoming increasingly different,” says Sales Manager Laurent Ratte. “As a consequence, a given model may be suitable for one kind of material, but not be relevant for another. For example, visco- plastic behaviour is well understood and described by current models. However, elasto-plastic behav- iour is underestimated, and existing models must be adjusted on a case-by-case basis.” Ratte says that material formulation, process set up and scale up are almost always performed today using the classic trial and error method, which means an important loss in terms of material, time and money. “We estimate that experimental development accounts for one-third of a R&D budget for a compounding company. Replacing this method by using numerical simulation is a
120 110 100 90 80 70 60 50 40 30 20 10 0
Torque/Shaft N.m
Figure 1: Comparison of torque values for different sets of operating conditions Image: SC-Consultants
www.compoundingworld.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62
