The first stage is the heating stage. You should put the tray with the materials into the oven without materials overlapping, so as to avoid unnecessary air leakage caused by the improper placement of the tray. Close the door of the drying box, and set the temperature in the box at 50 ℃ for 1.5-3 hours. When there is moisture in the box, you should start to drain the moisture for about 2 minutes. The temperature in the drying box will drop after the moisture is discharged, and the heating will continue.
The second stage is the constant-speed drying and moisture removal stage. This stage should be divided into two phases: (1) high humidity and low temperature phase, of which the temperature should be controlled between 55℃-60℃. You should avoid the color change of the material caused by high temperature and high humidity, and should observe the change of the water vapor on the surface of the material. Draining the moisture should keep for at least 3-3.5 hours.;and (2) medium humidity and medium temperature phase, of which the temperature should be controlled within 50℃-60℃. In this phase, the inlet valve can be properly opened and the return valve can be properly closed, which can be reasonably adjusted according to the moisture content.
The third stage is called speed reduction and setting stage, which is also known as low humidity and high temperature phase. The temperature should be keep at 70℃-80℃. It should not exceed 70℃ in the early stage, and should not exceed 80℃ in the later stage.