The auxiliary equipment of the extruder(2)

Preheating device(extruder)
Cable core preheating(extruder) is necessary for insulation extrusion and sheath extrusion. For the insulation layer, especially the thin-layer insulation, the existence of air holes is not allowed. The wire core can completely remove the water and oil on the surface by high-temperature preheating before extrusion. For the extrusion of sheath, its main function is to dry the cable core, Prevent moisture (or the moisture surrounding the cushion) makes it possible to have air holes in the sheath. Preheating can also prevent the residual internal pressure of the plastic due to sudden cooling during extrusion. In the process of plastic extrusion, preheating can eliminate the suspended temperature difference formed when the cold wire enters the high-temperature die and contacts the plastic at the die, so as to avoid the fluctuation of extrusion pressure caused by the fluctuation of plastic temperature, so as to stabilize the extrusion volume To ensure the extrusion quality. Electric heating wire core preheating device is adopted in the extrusion unit, which is required to have sufficient capacity and ensure rapid temperature rise, so that the wire core preheating and cable core drying efficiency are high. The preheating temperature is restricted by the setting out speed, which is generally similar to the head temperature.

Cooling system(extruder)
The formed plastic extrusion layer(extruder) shall be cooled and shaped immediately after leaving the machine head, otherwise it will deform under the action of gravity. The cooling method is usually water cooling, which is divided into rapid cooling and slow cooling according to different water temperatures. Quench is the direct cooling of cold water. Quench is beneficial to the shaping of plastic extruded layer. However, for crystalline polymers, due to sudden heat cooling, it is easy to residual internal stress in the extruded layer, resulting in cracking during use. Generally, quench is used for PVC plastic layer. Slow cooling is to reduce the internal stress of products. Water with different temperatures is placed in the cooling water tank in sections to gradually cool and shape the products. Slow cooling is adopted for the extrusion of PE and PP, that is, it is cooled in three stages: hot water, warm water and cold water.