REX – Computer-Aided Extruder Design

REX is a joint research project in which at the moment about 20 industrial companies and the KTP of the University of Paderborn participate. This software is a program to simulate manufacturing processes on single screw plasticizing units. The aim of the development is to enable the fast and global evaluation of the machine performance and consequently to be able to optimize the barrel and screw configuration as well as the process parameters. This aim is achieved mainly by the implementation of analytical and closed equations. Calculation-intensive numeric processes are avoided as far as possible.
Calculation possibilities

Currently, the following calculation possibilities are available in REX:

  • Pressure and throughput calculation
  • Melting calculation
  • Temperature profile calculation
  • Power consumption calculation
  • Residence times calculation
  • Calculation of the feeding process
  • Calculation of the mixing characteristic
(Figure 1: Graphical User Interface)
(figure 1: Graphical user interface)
In addition to the calculation of "pure" polymers, there are models implemented in PSI to estimate the behavior of polymer blends and polymer-filler compounds. Calculation process

In figure 2 the calculation process of REX is shown. The central element of a simulation is the pressure-throughput, the melting and the temperature calculation. These calculations serve as a basis for all further parameters to evaluate and optimize the screw configuration.
Bild 2: Berechnungsablauf
figure 2: Calculation process
Simulation results

The results of the simulation calculations can be either be shown in the form of diagrams or tables. The graphical output is created in such a way that the development of one parameter is illustrated along the screw length. Thus, it is possible to evaluate single screw zones. On the basis of these findings simple modifications at the screw design can be performed if necessary. Figures 3 and 4 exemplify the pressure profile respectively the melting profile of such a simulation calculation.
Picture 3: Pressure Profile
figure 3: Pressure profile along the screw length
Picture 4: Melting process (solid width, melting ratio)
figure 4: Melting profile (solid width, melting ratio)
To be able to calculate and evaluate the consequences of different parameters, a so-called variation module has been implemented in REX. In it all parameters that influence the process can be varied. All variations of the process are calculated and can afterwards be illustrated in a so-called multi graphic.
Further program functions

In addition to the real calculation REX offers further program functions, which support the user during the optimization.

Hence, it is possible to calculate one’s own functions in the form of user-defined functions. Here, the user can draw back on internally calculated values in order to determine his own company-specific characteristic values. This simplifies the calculation of the values in the way that, e. g., material characteristic values will always be chosen for each state of the process. As a further help, PSI contains a scale up module. It enables the user, for instance, to transfer the processes determined on small laboratory extruders onto a bigger production plant.

As a further function, REX offers a tool to a statistical experimental design (DoE). With it the relevant target and influencing parameters can be defined. Depending on the choice of the statistical model, the matrix is generated automatically and every operating point is calculated for the reduced experimental design. The connection of the results is then described with a regression model. This allows the user to evaluate the results graphically and to easily determine the operating point for the screw concept at hand.

Technical details:
Supported barrel designs

  • Smooth barrel, smooth barrel with feed supports, venting barrel

 Supported screw sections

  • Feed section, compression section, metering section, decompression section, barrier zone, wave zone, PIN-zone
  • Conical-shearing element, Maddock shearing element, Troester element, spiral shearing element, cylindrical shearing element; cross hole mixing element, rhombus-shaped mixing element, tooth mixing element
  • Annular non-return valve


For further information about REX, please contact Mr. Tobias Hallmann.

Demo

Anhänge
application/pdf iconREX-Flyer_English.pdf