The machine heater widely uses resistance heating, and uses thermocouples to realize segmented temperature control and detection. The resistance heating uses resistance to generate heat to the barrel, and then transfer the heat to the plastic in it. The method mainly includes strip heaters, cast aluminum heaters, ceramic heaters, etc., which have the advantages of small size, easy manufacturing and maintenance.
According to the different plasticization state of the material along the screw axis, the heating of the screw and the barrel must be carried out in sections to help improve the plasticization capacity in order to make the temperature distribution of the extruder barrel meet the process requirements. Generally, (3-5) Ds, (which is the screw diameter) is used as a heating temperature control section. The temperature control fluctuation range of heating should generally not exceed 5°C meanwhile for heat-sensitive plastics, the temperature should not be over 2°C.
When determining the heating power of the extruder screw barrel, it is also necessary to meet the requirements of productivity to ensure that the barrel has a sufficiently fast heating rate in addition to meeting the heat required for plasticization. The heating time of the machine is not more than 30 min for small machines, but generally about 1h for large and medium machines.
The design of cylinder cooling channel is adopted with a heat exchanger and a large stainless steel water tank. The cooling system shall choose softening water. Then, the cooling effect will be realized by controlling the flow of water in and out of the channel through the solenoid valve.