COMPUTATIONAL MODEL FOR A POLYMER EXTRUDER SCREW

Resumo

The most adequate process for an extrusive screw is the condition of operation. That involves the type of
polymer, the flow rate, mixture devices, temperature control and die. In view of productivity demands, e.g. flow
speed and filament homogeneity, it is deemed necessary a detailed study on the behaviour of the polymer along
the screw. This work aims at the development of a computational model, a tool which will be used on the design
of the screw of the extruder machine. Our model seeks to simulate the behavior of the material, providing enough
information for an adequate design for the screw, which is necessary in order to define the parameter for a viable
production.
The implemented model is based on the conservation of energy and moment equations, for which numerical
solutions are obtained through a projection method, where different boundary conditions are used for distinct stages
of the processes - feeding, metering and dosage. We simplify the process by considering a steady state regime on
a bi-dimensional domain. This characterizes a classical cavity problem. Since a rise of root diameter along the
axis is observed on most of commercial screws, this was the standard geometry adopted for the model. After
numerically solving the 2D Navier-Stokes equations, the pressure and velocity of the flow, which are obtained for
every stage, allow us to assess the efficiency of the process for the given geometry.