A stuffing screw (2) for use in an extruder system comprises a housing (7) and at least one conveying screw (5), which is mounted in a rotatable manner within the housing (7), wherein a conveying space is formed between an inner side of the housing (7) and the conveying screw (5). The stuffing screw (2) is characterized in that at least one portion of the inner side of the housing (7) is provided with one or more depressions, in particular in the form of a groove (13).

The invention discloses a central air extraction type pipe extrusion core mold assembly runner and a two-channel air extraction core mold assembly and belongs to the technical field of plastic pipe extrusion. The central air extraction type pipe extrusion core mold assembly runner comprises a core mold assembly and an extruder screw barrel; and a splitter plate arranged between the core mold assembly and the extruder screw barrel. The two-channel air extraction core mold assembly further comprises an air inlet pipe coaxial with the central air extraction pipe. The inner wall of a pipe product is cooled by way of air extraction by the central air extraction pipe, and the inner wall of the core mold assembly is cooled by way of air extraction by the in-mold cooling channel, thereby ensuring product quality and extrusion efficiency.