Process for manufacturing a cable, said 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 and a second annular flow of insulating material; • contacting the outer surface of said first annular flow and the inner surface of said second annular flow at an axial distance (x) from the contacting point where the inner surface of said first annular flow contacts the conductor; • selecting in combination said predetermined feeding speed and said contacting point, as a function of the dynamic viscosity (η) of the inner semiconductive material and of the insulating material, determined in accordance with the method outlined in the description, 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 contacting point, is comprised from 0.5 to 4; • compression extruding the insulating layer and the inner semiconductive layer onto the conductor. - 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, - 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 and a second annular flow of insulating material; • contacting the outer surface of said first annular flow and the inner surface of said second annular flow at an axial distance (x) from the contacting point where the inner surface of said first annular flow contacts the conductor; • selecting in combination said predetermined feeding speed and said contacting point, as a function of the dynamic viscosity (η) of the inner semiconductive material and of the insulating material, determined in accordance with the method outlined in the description, 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 contacting point, is comprised from 0.5 to 4; • compression extruding the insulating layer and the inner semiconductive layer onto the conductor. • providing a first annular flow of inner semiconductive material and a second annular flow of insulating material; • contacting the outer surface of said first annular flow and the inner surface of said second annular flow at an axial distance (x) from the contacting point where the inner surface of said first annular flow contacts the conductor; • selecting in combination said predetermined feeding speed and said contacting point, as a function of the dynamic viscosity (η) of the inner semiconductive material and of the insulating material, determined in accordance with the method outlined in the description, 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 contacting point, is comprised from 0.5 to 4; • compression extruding the insulating layer and the inner semiconductive layer onto the conductor.