A system for extrusion of material, for example chopped waste plastic, comprises a treatment device (101) for extruding the material and a feeder device (102) comprising a screw conveyor (103) for supplying the material to the treatment device. A screw element (104) of the screw conveyor has: a) a conical profile so that a diameter of the screw element decreases in a moving direction of the material and/or b) a thread-pitch decreasing in the moving direction of the material and/or c) an axial thickness of a screw thread crest increasing in the moving direction. The conical profile of the screw element and/or the thread-pitch decreasing in the moving direction and/or the axial thickness of the screw thread crest increasing in the moving direction improve the ability of the screw conveyor to compact the material and thereby to supply a sufficiently uniform material flow to the treatment device.

A resin extruder capable of efficiently improving performance of kneading a resin material is provided. A resin extruder (1) according to one embodiment includes a cylinder (20), and a rotor-type screw (33) that is disposed in the cylinder (20) and kneads a resin material (51). In the rotor-type screw (33), a top part (33b) of a flight (33a) is formed in such a way that a gap between the top part (33b) and an inner surface of the cylinder (20) is changed from a front point to a rear point of the rotor-type screw in a rotation direction in a cross section that is vertical to an axial direction.

A resin extruder capable of efficiently improving performance of kneading a resin material is provided. A resin extruder (1) according to one embodiment includes a cylinder (20), and a rotor-type screw (33) that is disposed in the cylinder (20) and kneads a resin material (51). In the rotor-type screw (33), a top part (33b) of a flight (33a) is formed in such a way that a gap between the top part (33b) and an inner surface of the cylinder (20) is changed from a front point to a rear point of the rotor-type screw in a rotation direction in a cross section that is vertical to an axial direction.