Development of an Experimental Facility to Test Polymer Extrusion

A wide variety of plastic profiles are produced in extrusion lines, which are basically comprised by an extruder, a die and a calibrator. Because the initial cooling stages will determine the final quality of the extrudate, the study of the thermal modeling of the calibrator is of great interest. In this context the use of computational tools is becoming increasingly useful for the calibrator design and optimization. Therefore, reliable experimental data is of paramount relevance to validate thermal models. For that purpose, an experimental apparatus was set-up at the laboratory, which includes: a calibrator, a heat chamber, a data acquisition system, a traction system and various polymer test samples. The experimental facility is designed to obtain data inside the polymer. Based upon computer simulations a calibrator was built in a aluminum alloy with 600×150×80 mm. The cross section aperture for the polymer profile is of 30×16 mm. Low inertia thermocouples were located at various positions and at depths varying between 1.0 to 5.0 mm from the calibrator/polymer interface. This is the region where greater thermal gradients are expected. Other sensors (at the surface) can be used to determine the interface thermal resistance. Data were collected by a high-speed data acquisition board (data a rate up to 500 kHz), with electronics for signal conditioning in order to compensate the low level signal of thermocouples. The data are stored for subsequent processing. All the process is controlled using an interface developed in LabView. Preliminary testes were carried out in PVC samples due to its high melting point and availability. The results proved the usefulness of the test facility to obtain relevant data concerning the thermal behavior of calibrators.