Jet streaks are traces that bend from the gate along the flow direction like a snake. It is caused by the high injection rate of resin from the gate. Therefore, it is an optional measure to expand the cross section of the fourth burner or reduce the injection speed. In addition, increasing the mold temperature can also slow down the cooling rate of the resin in contact with the cavity surface, which also has a good effect on preventing the formation of surface hardening skin at the initial stage of filling.