a plasticating apparatus adapted to handle a wide variety of synthetic resinous materials without predrying . the plasticating apparatus includes a two - stage screw rotatably and reciprocably mounted within a barrel . a surge suppressor is provided between the first and second stages and is comprised of an integral protrusion of the screw root and a deep channel section immediately preceding the protrusion . the surge suppressor prevents the surge of molten material into the vent area following the holding portion of an injection molding cycle , thereby allowing faster recovery and preventing bleeding of plasticized material from the vent opening .