Single-screw extruder with grooved infeed system

A single-screw extruder, comprising:

• a grooved infeed system;
• a cylinder having an inner cylinder wall;
• and
• an extruder screw rotatably supported in the cylinder and comprising in a processing direction a softening zone, a main plasticizing zone, and a post-plasticizing zone, said extruder screw having in the area of the main plasticizing zone at least two channels which are defined by channel depths which respectively vary in an undulating fashion and by wave crests in offset relationship,
• wherein the inner cylinder wall is provided in an area of the main plasticizing zone, at least partially, with at least one groove that essentially extends in a longitudinal direction,
• wherein the extruder screw has at least one screw thread which in the area of the main plasticizing zone is offset to form in front of each wave crest a gap of a gap height which corresponds to a channel depth of a respectively following one of the wave crests.