What is the heating and cooling setting of PE extruder
(1) Nowadays, extruders usually use electric heating, which is divided into resistance heating and induction heating. The heating element is installed in the body, neck, and head of the machine. The heating device heats the plastic inside the external heating cylinder to achieve the temperature required for process operation.
(2) The cooling device is set up to ensure that the plastic is within the temperature range required by the process. Specifically, it is to eliminate the excess heat generated by the shear friction of the screw rotation, in order to avoid excessive temperature that may cause plastic decomposition, burning, or difficulty in shaping. Barrel cooling can be divided into two types: water-cooled and air-cooled. Generally, air-cooled is more suitable for small and medium-sized extruders, while water-cooled or a combination of both forms of cooling are more commonly used for large extruders; Screw cooling mainly adopts central water cooling, aiming to increase the solid material conveying rate, stabilize the adhesive output, and improve product quality;
But the cooling at the hopper is to strengthen the conveying effect of solid materials, prevent plastic particles from sticking and blocking the material mouth due to temperature rise, and ensure the normal operation of the transmission part. 2、 The auxiliary equipment of the plastic extrusion unit mainly includes a pay off device, a straightening device, a preheating device, a cooling device, a traction device, a meter counter, a spark testing machine, and a winding device. The purpose of the extrusion unit is different, and the auxiliary equipment selected for it is also different. If there are also cutters, dryers, printing devices, etc. Straightening device: The most common type of plastic extrusion waste is eccentricity, and various types of bending of wire cores are one of the important reasons for insulation eccentricity.
In the extrusion of the sheath, scratches on the surface of the sheath are often caused by the bending of the cable core. Therefore, straightening devices are essential in various extrusion units. The main types of straightening devices are: drum type (divided into horizontal and vertical types); Pulley type (divided into single pulley and pulley group); Twisted wheel, serving multiple functions such as dragging, straightening, and stabilizing tension; Preheating devices such as roller type (divided into horizontal and vertical types): Cable core preheating is necessary for insulation extrusion and sheath extrusion. For insulation layers, especially thin layer insulation, the presence of pores is not allowed. The core can be thoroughly cleaned of surface moisture and oil stains by high-temperature preheating before extrusion. For the extrusion of the sheath, its main function is to dry the cable core and prevent the possibility of air holes in the sheath due to moisture (or moisture from the wrapping layer). Preheating can also prevent the residual internal pressure of plastic during extrusion due to sudden cooling.
During the plastic extrusion process, preheating can eliminate the significant temperature difference caused by the cold wire entering the high-temperature head and coming into contact with the plastic at the mold mouth, avoiding fluctuations in plastic temperature and extrusion pressure, thereby stabilizing the extrusion volume and ensuring extrusion quality. Electric heating wire core preheating devices are used in extrusion molding units, which require sufficient capacity and ensure rapid heating to achieve high efficiency in wire core preheating and cable core drying. The preheating temperature is limited by the wire release speed and is generally similar to the head temperature. Cooling device: The molded plastic extrusion layer should be cooled and shaped immediately after leaving the machine head, otherwise it will deform under the action of gravity. The cooling method usually adopts water cooling, and is divided into rapid cooling and slow cooling according to different water temperatures. Rapid cooling refers to the direct cooling of cold water. Rapid cooling is beneficial for the shaping of plastic extrusion layers, but for crystalline polymers, due to sudden heat cooling, internal stress is easily retained inside the extrusion layer structure, leading to cracking during use. Generally, rapid cooling is used for PVC plastic layers.
Slow cooling is used to reduce the internal stress of the product. Different temperatures of water are placed in sections in the cooling water tank to gradually cool and shape the product. Slow cooling is used for the extrusion of PE and PP, which involves three stages of cooling: hot water, warm water, and cold water.
