Problems Caused by Uneven Air‑Ring Air Output (Especially Obvious for Small / Mini Film Blowing Machines)
The air‑ring cools and sets the film bubble. Inconsistent air volume around the ring leads to uneven cooling intensity. Small‑size machines have tiny film bubbles, so they are far more susceptible to such issues than large‑scale machines.
1. Uneven film thickness (primary issue)
On sides with higher air volume: rapid cooling sets the melt quickly, resulting in thicker film.
On sides with ower air volume: slow cooling allows further stretching of the melt, resulting in thinner film.
Symptoms: One‑sided thickness difference around the film circumference, large circumferential thickness deviation, and uneven winding with bulging or concave edges.
2. Film‑bubble oscillation, wobbling and offset
Higher air pressure on one side pushes the bubble toward the low‑air‑volume side, causing back‑and‑forth shaking and lateral drift.
> Mini film blowing machines feature small bubbles; minor air imbalance can trigger bubble wobble. Cross‑draft in the workshop will worsen this condition.
3. Film surface wrinkles
Bubble wobble combined with uneven cooling misaligns the film before it enters the traction rollers, creating longitudinal and diagonal wrinkles that render finished films unusable.
4. Frequent film rupture and pinholes
Excessively fast local cooling hardens and embrittles the film, making it prone to tearing and bubble rupture under tension.
Insufficient local cooling leaves the film in a soft molten state, which gets easily pulled apart by traction and causes frequent film breaks.
5. Poor film surface quality
‑ Uneven cooling creates inconsistent gloss, with patchy bright and hazy areas on film surface.
‑ Water‑wave patterns and rough surface texture may occur.
6. Defective winding
Combined thickness deviation and bubble offset produce uneven winding: one side tight while the other loose, bringing bulging edges, curled edges and lotus‑leaf‑edge defects. Winding becomes irregular and subsequent slitting becomes difficult.
7. Unstable film bubble and narrow processing window
With uneven air‑ring airflow, the adjustable air‑volume range becomes very limited. Slightly increased air volume triggers bubble wobble or rupture; reduced air volume brings insufficient cooling. Stable production parameters are hard to achieve.
Common Causes of Uneven Air‑Ring Air Output
1. Partial blockage of air‑ring outlets by plastic scraps and debris
2. Tilted air‑ring installation, misaligned horizontally from the die center
3. Air‑duct air leakage leading to unbalanced air‑pressure distribution
4. Displaced or damaged internal guide vanes inside the air ring
5. Unstable air pressure supplied by the fan on small‑size machines
Simple Troubleshooting & Handling Tips
1. Regularly clean debris from air‑ring outlets
2. Keep the air‑ring level and concentric, aligned with the die center
3. Avoid excessive air volume; small machines prefer soft, low‑pressure cooling
4. Block workshop cross‑draughts to prevent external airflow from disturbing the film bubble
