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A theoretical model for the simulation of dynamic operation of a plasticating extruder is proposed. The model can be recommended as a tool to study various dynamic situations of interest in the operation of an extruder. Several responses to changes in operating conditions are discussed. They indicate the occurrence of transient maximas and occasional oscillations. The controlling of flow rate by adjusting a valve at the die seems to cause temporary local high peaks in pressure, whereas its control through screw speed seems to 'be satisfactory.

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A theoretical model for melting in reciprocating screw injection molding machines is proposed. The model permits the calculation of the solid bed profile as a function of time during the injection cycle. It consists of a dynamic extrusion melting model for the rotation period, a transient heat conduction model with a phase transition for the screw rest period, and a proposed model for the drifting of the beginning of melting during the injection cycle.he reciprocating screw injection-molding ma-