Solution to the Color Problem of Injection Molded Products

Causes of uneven color of injection molded products

The main reasons and solutions for the uneven color of injection molded products :

(1) Poor diffusion of the colorant, which often causes streaks near the gate.

(2) The thermal stability of plastics or colorants is poor. To stabilize the hue of the parts, the production conditions must be strictly fixed, especially the material temperature, material volume and production cycle.

(3) For crystalline plastics, try to make the cooling rate of each part consistent. Then, for parts with large wall thickness differences, colorants can be used to mask the color difference. For parts with uniform wall thickness, the material temperature and mold temperature should be fixed. .

(4) The shape of the part, the gate form, and the position have an impact on the filling of the plastic. Then, it causes some chromatic aberrationsome to parts of the part , which should be modified if necessary.

Causes of uneven color of injection molded products

Generally, the gloss on the surface of injection molded parts is mainly determined by the type of plastic, colorant, and finish of the mold surface. But there are some other reasons. The reasons and solutions are as follows:

(1) Poor mold finish, rust on the surface of the cavity, and poor mold exhaust.

(2) The gating system of the mold is defective. Then, we should enlarge the cold slug well and the runner, polish main runner, runner and gate.

(3) The material temperature and mold temperature are low. Then, the local heating of the gate can be used if necessary.

(4) The overly slow processing pressure and speed, the insufficient injection time and back pressure, these can result in poor compactness and dark surface.

(5) Plastics must be fully plasticized. But we need to prevent degradation of the material, stablize heating and adequately cooled, especially thick-walled ones.

(6) Prevent cold material from entering the part, use self-locking spring or lower nozzle temperature when necessary.

(7) Too much recycled materials are used. Plastics or colorants and lubricants are of poor quality. And water vapor or other impurities are mixed.

(8) The clamping force should be sufficient.

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