POWERFUL COMPUTER SIMULATION
FOR SINGLE SCREW POLYMER EXTRUSION
What is NEXTRUCAD?
NEXTRUCAD is a full-featured single-screw plasticating extrusion simulation package. The program simulates solids conveying, melting and metering in extruders. The solid bed profile, bulk melt temperatures and pressure build-up are predicted along the axis of the screw, along with the extruder output, power requirement, torque and average residence time. NEXTRUCAD is a successor, rather than an update, to Polydynamics’ earlier single-screw extrusion simulation software package EXTRUCAD.
NEXTRUCAD has been designed to be easy to use, with a simple and intuitive tabbed layout for inputs and outputs, and entry of values in English or SI units. The program is also flexible, with the user given the ability to fine-tune predictions based on available experimental measurements on an extruder. Context-sensitive help is accessible in the program, and handy tips are provided for specifying values for program control parameters.
NEXTRUCAD can be used to analyze the design of extruder screws and to examine the effect of rotation speed, barrel temperature profile, and material properties on extruder performance, without the line time and material consumption requirements of actually performing the runs. Extrusion engineers and even line operators can use it for "what ifs": what if the screw is changed, the material is changed, the operating conditions are changed, how will the operation of the extruder be affected? NEXTRUCAD is also useful as an educational tool for people new to extrusion, by giving insight into what happens within the black box of the extruder.
A unidirectional finite volume method is used. The equations employed include a form of Darnell and Mol's analysis for the solids transport zone, the Chung model of the Maddock-Tadmor mechanisms for the melting zone, and a mass and momentum transfer analysis in the "unwound" helical channel of the metering zone. All calculations can be performed using materials described with the Power Law or Carreau viscosity models.
NEXTRUCAD can be used for single-screw extruders with standard single-flighted screws, barrier screws of Maillefer / Uniroyal (variable width) and parallel flight (MC3 / Barr or Dray and Lawrence) designs, and screws with mixing (blister ring, Maddock or Egan) elements. Screw cooling and grooved feed extruders are also supported.
NEXTRUCAD predictions have been compared to experimental data available from university and industrial sources involving extruders with screw diameters of up to 150 mm (6 inches) and various types of screws, including barrier screws with mixing elements. Our predictions are in excellent agreement with the experimental data. The rigorous validation program is continuing and several refinements and improvements will be made to NEXTRUCAD for high precision analysis and design purposes.
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