Screw extruder

A screw extruder comprising:

• a pair of tapered screws arranged so as to approach each other toward a tip, each of the pair of tapered screws having a shaft portion and a wing portion spirally provided on an outer peripheral surface of the shaft portion and including a flat top surface;
• a driving device that generates driving force for rotating the pair of tapered screws;
• a casing that accommodates the pair of tapered screws and has an inlet for receiving a material and a passage port for allowing a material to pass therethrough;
• and
• a die plate attached to the casing so as to close the passage port, wherein the die plate includes a plurality of discharge perforations arranged at positions corresponding to the pair of tapered screws,
• positions and shapes of the plurality of discharge perforations are set such that size of an overlapping region of the top surface of the wing portion of each of the pair of tapered screws and a corresponding discharge perforation when viewed in a material extrusion direction periodically changes when the pair of tapered screws is rotated by the driving device, and
• a material extruded by the pair of tapered screws is cut by increase in the size of the overlapping region between the corresponding discharge perforation and the top surface of the wing portion.