(1) The exhaust of mold is not good, causing the plastic is adiabaticly compressed. Under high temperature and pressure, oxygen react violently, burning plastic.

(2) The die gate is too small.

(3) There are too many lubricants and demoulding agents in the material or in the mold. If necessary, the barrel should be cleaned regularly to remove antistatic additives.

(4) The size of nozzle hole, main channel and diversion channel is too small.