The heating of the machine adopts the way of resistance heating, and thermocouples are used for segmented temperature control and side detection. Resistance heating uses resistance to generate heat to heat the screw barrel, and then transfer the heat to the plastic in the barrel.
Resistance heating mainly includes strip heaters, cast aluminum heaters, ceramic heaters and so on. These heaters have the advantages of small size, easy manufacture and maintenance.
When determining the heating power of the twin-screw extruder barrel, in addition to meeting the heat required for plasticization, the productivity requirements of the injection molding machine must also be met to ensure that the barrel has a sufficiently fast heating rate. The heating time for small extruders is usually no more than 1 hour, and the heating time for medium and large machines is about 2 hours.
Under normal circumstances, the barrel is not equipped with a cooling control system, and natural cooling can meet the process requirements. However, if the temperature of the feed port is too high, "bridging" will occur at the feed port, making feeding difficult or even impossible.
In order to prevent the heat of the screw extruder barrel from being transferred to the transmission components, a cooling jacket (groove) should be set at the inlet of the barrel, and the cooling water volume should be adjusted according to the process requirements. In addition, when processing heat-sensitive plastics at high speeds, the machine must be cooled and temperature controlled to prevent the heat-sensitive plastics from being thermally decomposed.
