In the normal injection mold manufacturing process, the gloss of the mold surface is mainly determined by the type of plastic, coloring agent and the finish of the mold surface. The causes of dark color and poor luster and solutions are mainly as follows.

1. Poor finish of injection mold, rust on cavity surface, poor exhaust of mold.

2, the use of recycled material is too much, the quality of plastic or coloring agent is poor, mixed with water vapor or other impurities, the quality of the lubricant used is poor.

3, the injection mold gating system has defects, should increase the cold feed well, increase the flow channel, polishing main channel, diverter and gate.

4, the material temperature and mold temperature are low, if necessary, the local heating method can be used at the gate.

5, the plastic should be fully plasticized, but to prevent the degradation of the material, the heat should be stable, the cooling should be sufficient, especially the thick wall.

6, injection mold manufacturing process clamping force to be enough.

7, the injection mold processing pressure is too low, the speed is too slow, the injection time is insufficient, the back pressure is insufficient, resulting in poor compactness and dark surface.

8, prevent cold material into the parts, if necessary, use self-locking spring or reduce the nozzle temperature.

Do the above 8 points can be a good way to avoid the phenomenon of dark color and poor luster of the injection mold, even if this phenomenon occurs in the production process can also be a good remedy, to minimize the impact of the production schedule of the enterprise, increase the production efficiency of the enterprise.

Second, why do plastic mold products appear deformed

A series of plastic parts of different shapes and sizes can be processed by the coordinated changes of the convex and concave mold and the auxiliary molding system. In order to meet the needs of molded parts, we need to pay attention to some matters when choosing plastic molds, and put forward the corresponding needs. The following selection of a more suitable plastic mold needs to meet the following six requirements

1, high corrosion resistance Many resins and additives have a corrosive effect on the cavity surface, this corrosion makes the cavity surface metal corrosion, spalling, surface condition deteriorates, the quality of plastic parts deteriorates. Therefore, it is best to use corrosion-resistant steel, or chrome plating and nickel cymbal treatment on the cavity surface.

2. The gloss and precision of the surface of plastic products with good wear resistance are directly related to the wear resistance of the surface of plastic mold cavities, especially when some plastics are added with glass fibers, inorganic fillers and some pigments, they flow with plastic melt in the flow channel and mold cavity at high speed, and the friction on the surface of the cavity is great, if the material is not wear-resistant, it will soon wear out, causing damage to the quality of plastic parts.

3, good dimensional stability in the plastic molding, the temperature of the plastic mold cavity should reach 300℃ or more. For this reason, tool steel (heat-treated steel) that has been properly tempered is selected. Otherwise, it will cause changes in the microstructure of the material, resulting in changes in the size of the plastic mold.

4, easy to process mold parts are mostly made of metal materials, and some structural shapes are also very complex, in order to shorten the production cycle and improve efficiency, mold materials are required to be easy to process into the shape and accuracy required by the drawings.

5, polishing performance of good plastic parts usually require a good luster and surface state, so the surface roughness of the cavity surface is required to be very small, so the surface of the cavity must be processed, such as polishing, grinding, etc. Therefore, the selected steel should not contain rough impurities and pores.

6, the impact of heat treatment is small, in order to improve the hardness and wear resistance, the plastic mold is generally heat treated, but this treatment should make its size change is small. Therefore, pre-hardened steel that can be machined is used.