The auxiliary equipment of granulation unit mainly includes pay off device, straightening device, preheating device, cooling device, traction device, meter counter, spark testing machine and take-up device. The purpose of extruder is different, and its auxiliary equipment is also different. If there is a cutter, dryer, printing device, etc.
Eccentricity is one of the common types of plastic extrusion waste products, and the bending of various types of wire core is one of the important reasons for insulation eccentricity. In the extrusion of sheath, the scratch of sheath surface is often caused by the bending of cable core. Therefore, the straightening device in various extrusion units is essential. The main types of straightening device are: drum type (divided into horizontal type and vertical type); pulley type (divided into single pulley and pulley block); winch type, which plays a variety of functions such as driving, straightening and stabilizing tension; roller type (divided into horizontal type and vertical type), etc.
Core preheating is necessary for both insulation extrusion and sheath extrusion. For the insulation layer, especially the thin insulation layer, the existence of pores is not allowed. The moisture and oil on the surface of the wire core can be removed by preheating at high temperature before extrusion. For sheath extrusion, its main function is to dry the cable core and prevent the possibility of air holes in the sheath due to the effect of moisture (or moisture around the cushion). Preheating can also prevent the effect of residual internal pressure of plastics due to quenching. In the process of plastic extrusion, preheating can eliminate the large temperature difference formed when the cold line enters into the high temperature die head and contacts with the plastic at the die mouth, so as to avoid the fluctuation of the plastic temperature leading to the fluctuation of the extrusion pressure, so as to stabilize the extrusion amount and ensure the extrusion quality. The electric heating wire core preheating device is adopted in the extrusion line, which requires sufficient capacity and ensures rapid heating up, so that the wire core preheating and cable core drying efficiency are high. The preheating temperature is restricted by the pay off speed and is generally similar to the head temperature.