1. Insufficient injection and pressure holding pressure of injection molding machine; 2. The back pressure is too small and the raw materials are not solid enough;

3.背压太大,剪切、磨擦热量增加； 4.射速太慢,未充分结晶；

3. If the back pressure is too large, the shear and friction heat will increase; 4. Too slow shooting speed and insufficient crystallization;

5.模温太高,原料过火、分解、变质； 6.模温太低,未充分结晶；

5. The mold temperature is too high, and the raw materials are too hot, decomposed and deteriorated; 6. Mold temperature is too low and not fully crystallized;

7.射出、保压时间不足； 8.注塑机停机时间太长了和注塑周期太长；

7. Insufficient injection and pressure holding time; 8. The shutdown time of the injection molding machine is too long and the injection molding cycle is too long;

9.储料时间太长； 10.二级回料在新料里添加比例太多；

9. The storage time is too long; 10. The proportion of secondary return material in new material is too large;

11.原料强度、韧性不够，粘度不够； 12.添加剂不合理,或添加太多；

11. Insufficient strength, toughness and viscosity of raw materials; 12. Unreasonable additives or too many additives;

13.原料未充分烘干； 14.产品内部结构有些地方太厚，有些地方太薄，不均匀,进料地方考虑不合理。

13. Raw materials are not fully dried; 14. The internal structure of the product is too thick in some places, too thin and uneven in some places, and the consideration of feeding place is unreasonable.

15.模具进料不均匀,冷料井不够； 16.产品壁厚太薄

15. Uneven die feeding and insufficient cold well; 16. The product wall thickness is too thin

17.注塑机温度时高时低，不稳定； 18.注塑机料管没清理好；

17. The temperature of the injection molding machine is high and low, which is unstable; 18. The material pipe of the injection molding machine is not cleaned properly;

19.顶出不合理,塑体应力增加，产生破裂；

19. The ejection is unreasonable, and the plastic stress increases, resulting in fracture;

20.塑料件模具冷却回路没排好。

20. The cooling circuit of plastic mold is not arranged properly.