The injection molding process is incomplete because the cavity is not filled with plastic or the injection molding process lacks certain details.
A possible cause of the problem
(1) Insufficient injection speed.
(2) Plastic shortage
(3) There is no screw pad at the end of the trip.
(4) Variation of running time.
(5) The temperature of the charging cylinder is too low.
(6) Insufficient injection pressure.
(7) The shooting mouth is partially sealed.
(8) The heater outside the nozzle or injection cylinder cannot operate.
(9) Injection molding time is too short.
(10) Plastic is attached to the throat wall of the hopper.
(11) Capacity of injection molding machine is too small (i.e. injection weight or plasticizing capacity).
(12) Die temperature is too low.
(13) The anti-rust oil of the mold was not cleaned.
(14) The check ring is damaged and the molten material has backflow.