Cable manufacturing process

摘要

The present invention concerns a 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. The process comprises the step of co-extruding the inner semiconductive layer and the insulating layer. Said step comprises: a) providing a first annular flow of inner semiconductive material and a second annular flow of insulating material; b) contacting the outer surface of said first annular flow and the inner surface of said second annular flow at an axial distance from the contacting point where the inner surface of said first annular flow contacts the conductor; c) selecting in combination said predetermined feeding speed and said contacting point (D), as a function of the dynamic viscosity (η) of the inner semiconductive material and of the insulating material, so that a ratio between the shear stress of the inner semiconductive layer at the radially inner wall of the extrusion die and the shear stress of the insulating layer at the radially outer wall of the extrusion die, in proximity of said contacting point, is comprised from about 0.5 to 4; d) compression extruding the insulating layer and the inner semiconductive layer onto the conductor.