Abstract: Some helical grooves were cut on the inside of feeding sleeve, so that the barrel and the screw could be regarded as an integrated system to cooperatively convey the solid materials, thus a novel physical model known as "arc model" was formulated. At the same time, all the materials between the groove and channel were considered as a solid-plug, a novel solid conveying theory known as "double flight driving theory" was proposed, which filled out the flaw in the traditional extruder in the positive conveying. Finally, the boundary conditions in the crossover from friction drag to positive conveying and the design criterion of groove structure were given.

Key words: single-screw extruder, solid conveying, helical groove, double flight driving, positive conveying