1. Insufficient injection and pressure pressure of injection molding machine;
2. The back pressure is too small, the raw material is not solid;
3. The back pressure is too large, the shear and friction heat increase;
4. The shooting speed is too slow and not fully crystallized;
5. The mold temperature is too high, and the raw material is too hot, decomposed and metamorphic.
6. Mold temperature is too low and not fully crystallized;
7. Insufficient time for injection and pressure protection;
8. The machine downtime is too long and the injection cycle is too long;
9. The storage time is too long;
10. The secondary return material is too much added in the new material;
11. Raw material strength, toughness and insufficient viscosity;
12. Unreasonable additives or too many additives;
13. Raw materials are not thoroughly dried;
14. The internal structure of the product is too thick, some places are too thin, uneven, and the feeding place is unreasonable.
15. The mold feeding is not uniform, the cold well is not enough;
The product wall is too thin.
17. The temperature of injection molding machine is high and low and unstable;
18. The injection molding machine is not cleaned;
19. Unreasonableness of the roof and the increase of stress of plasticized body, resulting in rupture;
20. The mold cooling loop of plastic parts is not arranged.