the invention concerns an extruder , specifically a hand - held extrusion welding device . for the purpose of degassing a synthetic material to be extruded that is already partially plasticized in the extruder , the invention proposes a thread - less area between two screw threads of an extruder screw . the compression of the synthetic material to be extruded expels gas from the synthetic material , the expelled gas flows against the feeding direction , and exits from the extruder at a feed opening . the extruder proposed by the invention offers the advantage of a complete , or at least an almost complete , degassing of the plasticized synthetic material .