An extruder screw for a multi-screw extruder, having an intake and metering section. A rotor body has an enlarged diameter relative to the intake and metering section and has a plurality of satellite screws positioned on the outer periphery of the rotor body at least over part of the length thereof. A cone and an adjoining drive zone are formed between the intake and metering section and the rotor body, in which drive zone the satellite screws each engage via a drive pinion in an external toothing on the rotor body or in an internal toothing on a stator ring or in the inner wall of an extruder housing. At least one peripherally closed flow channel is formed, which flow channel extends from an inlet opening on the cone to an outlet opening located downstream of the drive pinions in the direction of flow.

A reciprocating blow molding unit includes an extruder screw foundation and an extrusion unit coupled to the extruder screw foundation. The extruder screw foundation includes a screw housing formed to include an interior cavity configured to receive polymeric material. The extrusion unit includes an extruder screw arranged to lie at least partially within the interior cavity and is configured to rotate about a longitudinal rotation axis to advance the polymeric material through the interior cavity.

An extruder has a pair of linkage parts configured to respectively link end portions of a pair of output shafts of the speed reducer with end portions of a pair of screws coaxially. The linkage parts each has: a coupling having an insertion hole into which the end portion of the screw and the end portion of the output shaft are inserted; and a locking part attached to the end portion of the output shaft. The coupling has a first receiving portion configured to receive the end portion of the output shaft; the second receiving portion configured to receive the locking part; and a step portion formed between the first receiving portion and the second receiving portion. As the step portion is locked by the locking part, a relative movement of the coupling relative to the output shaft in a direction towards the screw is restricted.