1. If the cavity of the injection mold is poorly processed, and there are some deficiencies, such as scars, micro holes, wear, roughness, it is bound to be reflected on plastic injection parts, making the plastic parts have poor luster. Therefore, the mold should be carefully processed to make the cavity surface have a small roughness, and if necessary, should be polished and plated with chrome.
2. If there are oil and water stains on the surface of the plastic injection mold and molding cavity, or too much mold release agent, the surface of the plastic part will be dark and dull. Therefore, the oil and water stains should be removed in time, and the release agent should be used in a limited amount.
3. If the demoulding slope of the plastic part is too small, it is difficult to demould, or the force during demoulding is too large, which makes the surface luster of the plastic part poor, so the demoulding slope should be increased.
4. If the exhaust of injection mold is not good, too much gas stays in the mold, which also leads to poor gloss. Therefore, the exhaust system of the mold should be checked and corrected.
5. If the cross-sectional area of gate or runner is too small or changes suddenly, the shear force acting on the melt is too large when it flows in it, which leads to turbulent dynamic flow, resulting in poor gloss. Therefore, the cross-sectional area of gate and runner should be appropriately increased.
1. If the injection speed is too slow, the surface of the plastic part is not dense, and the luster is poor. For this, the injection speed can be appropriately increased.
2. For thick-wall plastic parts, if the cooling is not enough, the surface will be hairy, and the luster is dark. Therefore, the cooling system should be improved.
3. If the packing pressure is not enough, the holding time is too short, so that the density of plastic parts is not enough, and the luster is bad. Therefore, the holding pressure and time should be increased.
4. If the melt temperature is too low, the fluidity is poor, which leads to the poor luster. Therefore, the melt temperature should be increased appropriately.
5. For the plastic parts made of crystalline resin, such as PE, PP, and POM, if the cooling is not uniform, it will lead to poor gloss. Therefore, for example, the cooling system of such pom injection molding should be improved to cool it evenly.
6. If the injection speed is too high and the cross-sectional area of gate is too small, there will be dark and poor luster near the pouring. Therefore, the injection speed can be appropriately reduced and the cross-sectional area of gate can be increased.