Injection moulds causes of surface defects

Injection molds must be used to produce plastic injection products,. In general, the produced by the method of injection molding plastic products surface gloss and color is very good, but sometimes there will be some shortcomings. In addition to the material of plastic, colorant, mould surface gloss, what reason can cause such effects in the injection?
( 1) The mold finish is poor, cavity surface rust, etc. , and mold venting is not good.
( 2) Mould gating system has a problem, need to increase the cold well, sprue, polishing sprue, runner and gate.
( 3) Material temperature and mold temperature is low, if necessary, can adopt the method of gate local heating.
( 4) Injection molding process pressure is too low, too slow, injection time, back pressure is not enough, leading to poor compactness, black surface.
( 5) Plastic should be completely plasticizing, but should prevent material degradation, heating should be stable, cooling should be fully, especially thick wall.
( 6) To prevent cold material into parts, if necessary, switch to the self-locking spring or lower the temperature in the nozzle.
( 7) Recycled material use too much, plastic or poor quality of colorant, mixed with water vapor or other impurities, the use of lubricant quality is poor.
( 8) Clamping force should be enough.