Apparatus for extruding a pliable, thin-walled tube comprising an extrusion and shaping die assembly comprising an annular die body, a mandrel supported within the annular die body, a mandrel extension mounted on the mandrel adjacent the die outlet, the mandrel extension having a diameter less than the...http://www.google.de/patents/US4828770?utm_source=gb-gplus-sharePatent US4828770 - Extrusion system
