1, the heating time is too long, the accumulation of heating, resulting in aging and burning of plastic.

2, after many times of color change, so that the decomposition of the plastic itself caused the phenomenon of burning.

3, the temperature control itself of the instrument failure, resulting in high temperature resulting in burning.

4. The gland is not tightly covered, leading to the aging and decomposition of the plastic.

5, the screw did not do regular cleaning, resulting in the accumulation of burning objects.