The Twin-Screw Extruder Simulator (TXS™) is a personal computer software package for process simulation and analysis of plastics compounding operations in corotating, intermeshing, modular twin-screw extruders.
TXS allows you to obtain quick approximate answers to many processing problems that arise in the compounding plant and the process development laboratory.
TXS simulates all the steps in the process: solids conveying, melting, mixing, melt conveying, pressurization, and die flow. The simulations are performed in realistic settings, with multiple feed and vent ports.
TXS can simulate complex processing operations, such as the extrusion compounding of filled compounds, reinforced materials, elastomer-plastomer blends, color concentrates, etc.
TXS may be used for specific process applications wherever corotating twin-screw extruder are employed: in the farmaceutical and cosmetics industries, in food processing, etc.
Some of the main features of TXS are:
- Fully graphical extruder configuration. Assemble your screw by clicking on screw elements and barrel sections within a graphical palette of available options. Modify existing configurations, add or delete components, etc. while viewing a complete picture of the screw.
- Full support of most extruder components. Support for closed and open, top and side-fed barrel sections, single, double and triple-flighted screw conveying elements, kneading blocks, slotted mixing elements, gear and blister rings, breaker plates, screen packs, strain dies, etc. Including many non-standard components.
- Easy setup of operating conditions. Select resins and fillers from a customizable database; input rate, speed, feed conditions; set the barrel temperature profile and feed protocol (for multi-component, multi-port systems). All in one simple graphical screen.
- Processing options. Use different melting and heat transfer models for a more realistic evaluation of the extruder’s processing characteristics, or simulate the effect of screw wear on your process.
- Ultra-fast simulation engine. Typical simulations take under one second in an entry-level Pentium system.
- Full control of the process models and numerical procedures. TXS gives users full control of the process model though the use of adjustable coefficientes and debugging aids. Most steps of numerical procedures (initial guesses, iteration criteria, tolerances, etc.) are also under user control, with a complement of intermediate output options to verify performance.
- Rule-based “expert system”. TXS analyzes your screw before running a simulation and advises you of potential problems. After a simulation is performed, TXS analyzes the results, detects problems, and tells you what is wrong and how to correct it.
- Summary of Results. Display (and print) tables of global processing parameters that help you evaluate your process: residence time, discharge temperature, power consumption, specific energy input, etc.
- Axial Plots. Plot (and print) the values of most important processing variables along the screw: pressure, temperature, fill factor, power, torque, unmolten solids, etc. Plot the results of different simulation runs in a single plot using TXS’s Multi-Plot option for easy trending and comparison.
- Interactive heat transfer and mixing analysis tool. Get key heat transfer parameters barrel by barrel, and key dispersive and distributive mixing parameters, mixing section by mixing section. Get the overall residence time distribution (RTD) function. Compare residence time; shear rate and shear stress, extensional flow components, mixing indices, etc.
- Materials Editor. Add new materials specifications for resins, solid and liquid additives, and polymer blends, or modify existing ones, using the separate fully graphical utility program, the TXS Materials Database Editor (TXM), provided with the TXS package.
- Multiple output options. Print results summaries, text reports, screw configurations, axial plots. Export extruder configurations to high-resolution graphics files for insertion into documents and presentations. Export a table of processing variables for use with third-party graphics or spreadsheet software.
The speed and ease of use of TXS allows you to play “what-if” scenarios with many processing variations, and perform quick and inexpensive “computer experiments” to screen screw configurations for new materials, optimize operating conditions, etc. TXS is also a valuable learning tool to complement training programs in extrusion theory and practice. Designed with a highly modular structure, it can be easily customized. Adding new screw elements or processing options, modifying computational algorithms or changing the displays can be easily accomplished.
An important characteristic of TXS is its graphical approach to assembling and viewing extruder configurations. Components are represented and manipulated as schematic, but easily recognizable and dimensionally accurate, drawings of the actual parts. The barrel and screw are realistically assembled on the screen, thanks to TXS’s simple point-and-click interface. This makes TXS a powerful visualization tool for twin-screw extrusion. The different functional zones of the screw (solids conveying, melting, mixing, venting, pressurization, etc.) are immediately recognized. Screw/barrel alignment can be judged at a glance and different configurations are easily compared.
Behind the speed and “user friendliness” of TXS is a state of art computer simulation engine. Although based on well known “one-dimensional” models, TXS improves on them through the use of structured axial elements. In this way, important phenomena such as heat transfer in flight clearances and elongational flow components in the intermesh region can be approximated and incorporated to the model. TXS uses an original blend of “theoretical” analytical models, semi-empirical correlations, and adjustable parameters to improve its performance. Using this technique, the simulation engine can “tuned up” for specific extruders, materials, or processes.
When using TXS, you should be aware that its computations are approximate. TXS has been validated using available experimental data to ensure that its results are not far off the mark. However, as any process simulation software, TXS must balance accuracy and computational efficiency. Other computational solutions may be available that will provide more accurate and detailed answers to some problems, but none will be able to simulate the whole extruder from feed throat to died exit as TXS does. Moreover, these solutions are significantly slower, and require a heavy commitment in hardware and personnel resources. If you need these tools, TXS can help you minimize their drawbacks, by screening possible alternatives and providing initial estimates.
The program is constantly being improved and new features are regularly incorporated. Some of them, currently under development at PolyTech, are:
Devolatilization. A module to simulate the removal of solvents and other volatile impurities from polymer melts during extrusion is also under development. The new module will permit the simulation of multi-stage, multi-component devolatilization operations, and the use of stripping agents, such as inert gases, steam, pressurized liquid water, etc. The Materials Database will be extended to include volatile components.
Reactive Processing. Due to the nature of reactive extrusion, these modules are developed and incorporated on demand, in customized versions of the software.
TXS was developed by Dr. Eduardo L. Canedo (PolyTech) and validated with computational and experimental data provided by the Polymer Processing Institute (PPI, then at Hoboken, NJ). For questions, comments or suggestions please contact TXS distributor: