(1) poor mold finish, mold surface rust, mold exhaust is bad.
(2) if the casting system of the mold has defects, the cold feed well should be increased, and the flow passage, polishing mainstream passage, diversion passage and gate should be increased.
(3) the material temperature and mold temperature are low, if necessary, local heating method of gate can be used.
(4) low processing pressure, slow speed, insufficient injection time, insufficient back pressure, resulting in poor compactness and dark surface.
(5) plastic should be fully plasticized, but to prevent the degradation of the material, heat should be stable, cooling should be sufficient, especially thick wall.
(6) to prevent cold materials from entering the workpiece, use self-locking spring or lower nozzle temperature when necessary.
(7) excessive recycled materials, poor quality of plastics or colorants, mixed with water vapor or other impurities, poor quality of lubricants used.