An evaluation of the efficiency of the plasticating systems in the extrusion process. Part II. Computational methods for the efficiency evaluation

As fundamental criteria for the evaluation of the efficiency of the plasticating systems of extruders have been chosen efficiency and cost of the extrusion process and product quality. In the last mentioned category, the effect of the process parameters (temperature, pressure and flow rate) with consideration of their variability in time, the effect of the uniformity of material composition (quality of intermixing) and the effect of rheological behavior of material (viscosity and elasticity) have been treated separately. A review of the computational methods for the efficiency evaluation has been made. The direct methods basing on the computation of quantities assumed as the efficiency criteria directly from the mathematical model of the process and the indirect methods basing on some selected measures characterizing quantities serving as those criteria have been distinguished. It has been demonstrated that up to now the direct computational methods are unable to evaluate the variability of temperature, pressure and flow rate as well as the quality of material intermixing. For such evaluation the indirect methods are used.