Bubbles:
Bubbles and voids are cavities formed inside molded products. There are two types of bubbles: one occurs when the product cools and shrinks — as the surface hardens, the thicker areas inside form hollow voids known as vacuum bubbles; the other type occurs when moisture, volatile substances, or air trapped in the resin enter the cavity with the melt during molding and become enclosed inside the molded product as small bubbles.
| 8.1 Causes | 8.2 Solutions |
|---|---|
| 8.1.1 Raw material contains moisture, solvents, or volatile substances. | 8.2.1 Replace with qualified material and dry according to specifications. |
| 8.1.2 High melt temperature or long heating time causes plastic degradation. | 8.2.2 Control appropriate melt temperature and heating time to prevent material decomposition and gas formation. |
| 8.1.3 Low injection or holding pressure. | 8.2.3 Increase injection and holding pressure to expel gas from the cavity and melt. |
| 8.1.4 Early screw retraction or short holding time. | 8.2.4 Ensure sufficient injection and holding time to prevent vacuum bubbles from shrinkage. |
| 8.1.5 Poor mold venting. | 8.2.5 Add vents at appropriate positions in the mold. |
| 8.1.6 High screw speed and low back pressure. | 8.2.6 Reduce screw speed and increase back pressure. |
| 8.1.7 Low mold or melt temperature. | 8.2.7 Increase mold and melt temperature to ensure proper compensation for shrinkage. |
| 8.1.8 Injection speed too fast. | 8.2.8 Adjust injection speed to avoid turbulence that traps air. |
| 8.1.9 Moisture, oil, or improper release agent inside mold cavity. | 8.2.9 Clean moisture and oil from cavity and use a proper release agent. |
| 8.1.10 Too fine or uneven pellets, low back pressure, or air entrained at the hopper or feed end. | 8.2.10 Use appropriately sized pellets, maintain good feeding, control barrel temperature, and prevent bridging to avoid air entry. |
| 8.1.11 Poor part or runner design causing trapped air pockets. | 8.2.11 Add vents at appropriate locations and inject at slower speed. |
| 8.1.12 Nozzle diameter too small. | 8.2.12 Use a nozzle with a larger diameter. |
| 8.1.13 Hot runner temperature too high or thermocouple malfunction causing material decomposition. | 8.2.13 Reduce hot runner temperature or replace faulty hot runner components. |
follow us :
-- get updates with latest topics
e-mail
English
français
Deutsch
русский
italiano
español
português
العربية
日本語
한국의
中文