The cooling process of crosslinked polyethylene from the die extrusion has the factors that may lead to the surface quality of the insulating core. (1) The cable surface is accompanied by bubbles, when the cable enters the water, if the surface of the air bubble attachment, the position will be cooled after the "small pit bag", this is because the bubble will be wrapped in the atmosphere of the insulating surface, the bubble cover part of cooling faster than with the water contact part of the slow.

The formation of air bubbles attached to the surface of the cable is generally the cooling of the circulation of water into the tank when the flow of fast, rapid flow, high-speed flow of air into the water, a part of the air attached to the cable surface, forming bubbles; (2) before entering the cooling water droplets splash in the cable surface, and the water contact part of the first cooling contraction, and air contact with the part of the High-temperature state, due to the difference in cooling speed of the insulation core surface uneven phenomenon.