Patent ID: 7811494

Claim:
A process for manufacturing a cable comprising: a conductor; an inner semiconductive layer surrounding said conductor and having a thickness lower than or equal to 0.4 mm; and an insulating layer surrounding said inner semiconductive layer, said process comprising the steps of: feeding the conductor at a predetermined feeding speed to an extrusion head comprising a first extrusion channel for extruding the inner semiconductive layer and a second extrusion channel for extruding the insulating layer, said first extrusion channel and said second extrusion channel being separated from each other by a first extrusion die; and co-extruding the inner semiconductive layer and the insulating layer, said step of co-extruding comprising: providing a first annular flow of inner semiconductive material in fluid form and a second annular flow of insulating material in fluid form; contacting the outer surface of said first annular flow and the inner surface of said annular flow at a first contacting point while maintaining said materials in fluid form at an axial distance from a second contacting point where the inner surface of said first annular flow contacts the conductor; selecting in combination said predetermined feeding speed and said first contacting point as a function of the dynamic viscosity of the inner semiconductive material in fluid form and of the insulating material in fluid form, so that a ratio between the shear stress of the inner semiconductive layer at the radially inner wall of said first extrusion die and the shear stress of the insulating layer at the radially outer wall of said first extrusion die, in proximity of said first contacting point, is about 0.5 to 4; and compression extruding the insulating layer and the inner semiconductive layer onto the conductor.