Method and device for the continuous extrusion of rods made of plastic raw material equipped with a helical inner channel

摘要

A continuous extrusion process and device are disclosed for rods made of a plastic raw material and provided with at least one inner channel which at least in part is spiral-shaped. The raw material may be a powder-metallurgical or ceramic mass. The plastic raw material is extruded through a nozzle mouthpiece and made to rotate by means of an arrangement of flow guiding surfaces provided therein, entraining at least one thread made of a flexible or elastic material and giving it a spiral shape with a predetermined pitch. The thread is retained upstream of the nozzle mouthpiece in an eccentric position relative to the rod axis and extends through the nozzle mouthpiece. In order to improve production accuracy and production tolerances of the extruded rod blank while simplifying the corresponding device, the movement of rotation of the plastic raw material is adjusted by an outer adjusting force which modifies the angle between the arrangement of flow guiding surfaces and the longitudinal axis of the nozzle mouthpiece in order to adjust the position and/or the pitch of the at least one inner spiral channel.