Process analysis of plastication & purging in reciprocating screw injection molding

Plastication and purging of resin in injection molding and other plastic fabrication processes is an essential requirement of manufacturing. A reciprocating screw injection molding machine uses a rotating screw to plasticate the material followed by a plunger action to inject the melt.;This paper provides a review and analysis of the governing principles that cause an oscillating change in a tracer concentration in the resin during plastication and purging. Experimental studies done by Dirk Schmiederer and Wipoo Sriseubsai were critically analyzed for the time varying decay in concentration during purging after a step change in input concentration.;The reciprocating screw injection molding machine is compared to a "tanks in series" model as described by Octave Levenspiel. The results of the study indicate that a higher order system which is described by a second order or higher order differential equation is required to describe the resin changeover in injection molding.