Causes of surface defects that affect injection molding


Generally, plastic products produced by this injection […]

Generally, plastic products produced by this injection molding method have good gloss on the surface. It is the same as color, but sometimes there are some disadvantages inevitably. In addition to the material problems of the plastic itself, the colorant and gloss of the mold surface, what other reasons can the injection molding process cause?

(1) The mold finish is poor, the cavity surface is corroded, and the mold exhaust is not good.
(2) There is a problem with the gate system of the mold. Cold bullet wells should be added, and runners, polished sprues, runners and gates should be expanded.
(3) The material temperature and mold temperature are low, and the gate can be locally heated if necessary.
(4) The injection molding process pressure is too low, the speed is too slow, the injection time is insufficient, the back pressure is insufficient, the compactness is poor, and the surface is blackened.
(5) Plastics must be completely plasticized, but material degradation must be prevented, heating must be stable and cooling must be sufficient, especially for thick-walled materials.
(6) Prevent cold materials from entering the workpiece, and use self-locking springs or lower the nozzle temperature when necessary.
(7) Too many recycled materials are used, the quality of plastics or colorants is poor, water vapor or other impurities are mixed, and the quality of lubricants used is poor.
(8) The clamping force should be sufficient. The difficulty of mold release for injection molders is mainly because the gate or plastic parts are tightly packed in the mold. Reasons: 1. Equipment: insufficient ejection power.
2. Mold (1) The demolding structure is unreasonable or the position is incorrect. (2) The draft angle is insufficient. (3) Mold temperature is too high or poor ventilation. (4) The runner wall or cavity surface is rough. (5) The nozzle does not meet the mold entrance or the nozzle diameter is larger than the entrance diameter. 3. Treatment (1) The temperature of the barrel is too high or the injection volume is too large. (2) The injection pressure is too high or the holding and cooling time is too long. 4. Raw material: insufficient lubricant. The traditional demolding methods of plastic molded parts are roughly divided into four types: push, push, pull and rotate. Now there is a newest demoulding technology that can easily solve the problem of plastic demoulding. In the plastic mold industry, there are many unsolvable problems, especially when various resin compounds are used for highly complex designs and high gloss surface treatments.