Bubbles are the phenomenon of small volume or series of pores formed inside the product. A large amount of gas is mixed into the melt and is formed by cooling the melt.
1. Venting system is bad or blocked
2. The cooling system is not setting properly, which makes the material cooling uneven or insufficient.

3. The injection speed is too fast
4. The material temperature is too high, which will cause the material to degrade and generate a lot of gas
5. The material temperature is too low, and the fluidity is poor, which will cause insufficient filling.
6. Insufficient holding pressure or time

7. It has a lot of water content and generates a lot of gas when heated.
8. Recycled material is added too much, because there are more impurities in recycled material
9. More volatile substances