“…Temporal thermal variations of melt output may cause to generate variations of melt pressure resulting in output rate variations, non-uniformities of optical/mechanical/chemical properties of the extruded parts, extrudate with un-melted particles, etc [7]. In fact, process problems can occur due to the variability of processing materials [8,9,10], machine geometry [11,12,13,14,15] and process settings [4,8,13,16,17]. Obviously, the processing problems attributed to the machines' functionality (e.g., screw misalignments, vibrations of machine parts, inaccuracies of screw design) have to be addressed at the stage of machine design and the selection of optimum operating conditions may be the most important factor to achieve process requirements for a given machine and a material.…”