Electric resistance heating is widely used in machine heating, and thermocouples are used to achieve segmented temperature control and side detection. Resistance heating is to use resistance to generate heat to heat the barrel, and then transfer the heat to the plastic in the screw barrel
. Resistance heating mainly includes strip heaters, cast aluminum heaters, ceramic heaters, etc. These heaters have the advantages of small size, ease of manufacture and maintenance.
According to the different plasticizing states of the material along the screw axis, in order to make the barrel distribution meet the requirements of the injection molding process, the heating of the screw machine must be carried out in stages to improve the plasticizing capacity. Generally, (3-5) Ds, (Ds is the rod diameter) is a heating temperature control section, and the heating temperature control fluctuation range should generally not exceed 5 °C, and should preferably not exceed 2 °C for heat-sensitive plastics.
Extruder screw barrel heating power
When determining the heating power of the barrel, in addition to the heat required for plasticization, it is also necessary to meet the requirements of the productivity of the injection molding machine to ensure that the barrel has a sufficiently fast heating rate. The heating time of the machine heating is not more than 30min for small machines, and is generally about 1h for large and medium-sized machines.
Cooling of Extruder Screw Barrel
① Under normal circumstances, the barrel does not need to be equipped with a cooling control system, and the process requirements can be met by natural cooling. However, if the temperature of the feeding port is too high, the phenomenon of "bridging" will appear at the feeding port, making feeding difficult or even impossible.
② In order to ensure good feeding and conveying conditions of solid materials and prevent the heat of the barrel from being transferred to the transmission parts, a cooling jacket (slot) should be set at the feeding port of the barrel, and the cooling water volume can be adjusted according to the process requirements. In addition, when heat-sensitive plastics are processed at higher speeds, the machine must be cooled and temperature-controlled to prevent thermal decomposition of heat-sensitive plastics.