Analysis of color dullness

The glossiness of the surface of injection molded parts is primarily determined by the type of plastic, colorant, and the smoothness of the mold surface. However, defects such as surface color and gloss imperfections, as well as darkened surfaces, often occur due to various other factors. The causes and solutions for these issues are analyzed as follows:

(1) The mold has poor surface finish, with rust on the cavity surface, and poor mold venting.

(2) The gating system of the mold has defects. It is recommended to increase the size of the cold well, expand the runner, and polish the main runner, branch runners, and sprues.

(3) If the material temperature and mold temperature are relatively low, local heating through the sprue may be applied when necessary.

(4) Poor compactness due to excessively low processing pressure, slow speed, insufficient injection time, and inadequate back pressure, resulting in a dark surface.

(5) Plastics should be fully plasticized, but care should be taken to prevent degradation of the material. They should be heated stably and cooled thoroughly, especially for those with thick walls.

(6) To prevent cold material from entering the molded part, use self-locking springs or reduce the nozzle temperature when necessary.

(7) Excessive use of recycled materials, poor quality of plastic or colorant, presence of moisture or other impurities, and poor quality of lubricant used.