Common defect causes and treatment methods of the

Common defect causes and treatment methods of compression molded products

1) blistering on the surface and internal uplift of plastic parts

① the content of moisture and volatile matter in molding materials is too high. Pre drying and preheating shall be carried out

② the mold temperature is too high or too low. It should be adjusted appropriately

③ the forming pressure is too low. It should be improved appropriately. Generally, for every 1mm increase in thickness, the molding pressure should be increased by 2MPa

④ poor mold exhaust. Exhaust conditions should be improved

⑤ the compression ratio of molding compound is too large and the air content is too much. The blank shall be pre pressed

⑥ improper control of holding time. It should be adjusted appropriately. Generally, the heat preservation time should be appropriately longer

⑦ the curing time is too short. It should be extended appropriately

2) the surface of plastic parts is gray

① the mold temperature is too low. Only by properly improving the real manufacturers can it be very cheap

② the surface of the mold cavity is rough. The surface finish of the cavity should be improved

③ the amount of lubricant is too much and should be appropriately reduced

④ improper use of release agent. Appropriate release agent shall be selected

3) high strength steel wire and steel strand for prestressed concrete with plastic surface spots BS 5896 ⑴ 980 points

① impurities are mixed in the molding compound. It should be completely removed

② the content of moisture and volatile matter in molding materials is too high. Pre drying and preheating shall be carried out

③ the particle size of raw materials is very different, and the large particle resin is poorly plasticized and adheres to the surface of plastic parts. Resin with uniform particle size shall be selected

④ the surface of the mold cavity is rough. It should be polished to improve the surface finish of the cavity

⑤ the mold cavity is not clean. The cavity should be cleaned

4) plastic part surface paste spots

① the mold temperature is too high. It should be reduced appropriately

② improper preheating of molding compound. Prevent under preheating or over preheating. The preheating temperature and time shall be subject to the best fluidity

③ mold closing speed is too slow. It should be accelerated appropriately

5) orange peel lines on the surface of plastic parts

① improper mold closing. The mold should be closed slowly under low pressure. Generally, the mold can be closed after loading. When the punch does not touch the molding powder, it should be closed quickly; It should be closed slowly after touching the molding powder

② the mold temperature is too high. It should be reduced appropriately

③ improper preheating of molding compound. High frequency preheating shall be carried out

6) flow marks on the surface of plastic parts

① the fluidity of molding compound is too good or the content of moisture and volatile matter is too high. The molding compound should be replaced or pre dried and preheated

② improper use of release agent. The appropriate type of release agent should be selected and the dosage should be appropriately reduced

③ insufficient loading. When loading, the appropriate feeding method should be determined according to the shape of the plastic part and the mold structure. Where it is difficult to fill, it should be loaded more or more times

④ the exhaust time is improper or too long. The timing and time of exhaust shall be properly controlled

7) uneven color or discoloration on the surface of plastic parts

① poor thermal stability of molding materials. New materials should be used

② the molding temperature is too high, and the melt or colorant is overheated and decomposed. The pressing temperature should be properly reduced

③ molding compound preheating does not automatically return to the vehicle - it is good when it is set to lock simply and set to return to the vehicle. Appropriate preheating method, preheating time and temperature shall be selected