What are the conditions and methods of using the screw and barrel of the plastic extruder

Many plastic products we see in our lives are made of plastic extruders. As an important part of plastic extruders, it is necessary to master the conditions and methods of its use. Today we will focus on its heating method, temperature control range, heating power, cooling and other aspects of knowledge.

Heating method of screw and barrel

At present, most of the barrels of plastic extruders are heated by resistance heating, and thermocouples are used to achieve segmental temperature control and side detection. The main principle of resistance heating is to use the heat generated by the resistance to heat the barrel, and then transfer the heat to the plastic in the barrel.

The equipment required when using resistance heating is cast aluminum heater, strip heater and ceramic heater, etc. These heating equipment have the characteristics of small size and convenient use.

The temperature control range of the barrel

According to the different plasticization states of the material along the axis of the screw, the temperature required for the barrel is different. In order to make the barrel distribution meet the actual requirements of the injection molding process, the heating used in the screw machine should be carried out in stages, and the staged heating can also improve the plasticizing capacity.

Generally speaking, (3-5) Ds, (Ds is the diameter of the rod) belongs to the heating temperature control section, and the heated temperature should not exceed 5 °C when controlling the fluctuation range. If the material used is heat-sensitive plastic , the temperature fluctuation cannot exceed 2°C.

Heating power of screw and barrel

When determining the heating power of the barrel and screw, it is not only necessary to consider the heat required for plasticization, but also to meet the productivity requirements of the plastic extruder to ensure that the barrel has sufficiently fast heating rate.

Generally speaking, the heating time of ordinary equipment heating does not exceed 30min. If it is a large equipment or a central equipment, the heating time is about 1h.

Cooling of screw and barrel

In most cases, the Conical twin screw barrel does not need to be equipped with a cooling control system, and only needs to rely on its own natural cooling to meet the requirements of the production process. Once the temperature of the feeding port is too high, it will cause obvious "bridging" phenomenon at the feeding port. In the subsequent processing, it will be difficult to feed, and in severe cases, it may not even be possible to feed.

In order to ensure a relatively good feeding and conveying conditions of solid materials and avoid transferring the heat of the barrel to the transmission parts, a cooling jacket (slot) should be installed at the feeding port of the barrel, according to the temperature requirements of the processing technology. , adjust the size of the cooling water flow.