Patent ID: 8585949

Claim:
A method for extruding a polymeric material comprising the steps of: feeding said polymeric material to an extrusion apparatus comprising an extrusion head, said extrusion head comprising: a male die; a female die coaxially arranged with respect to said male die, wherein one die of said male die and said female die is axially displaceable with respect to the other die along an axial direction of said extrusion head; a conveying channel, at least one portion of which is defined between said male die and said female die; and adjusting a cross-sectional area of said at least one portion of the conveying channel by reciprocally displacing said female die with respect to said male die in response to an extrusion speed variation of said polymeric material, including passively displacing said axially displaceable die with respect to the other die along said axial direction by a spring force exerted by a resilient element; wherein the magnitude of the spring force is substantially equal to a force exerted by the polymeric material acting on the female die.