How to solve film breakage of PE blown film machine?

Film breakage is one of the key failures limiting productivity and raising material consumption in PE blown film production. Its causes involve multiple factors including material properties, equipment status, process parameters and ambient conditions. Targeted inspection and troubleshooting are required. Details are as follows:

1. Material: Stabilize basic properties and eliminate latent defects

Melt strength and purity of PE materials are fundamental for preventing film breakage. Materials with insufficient melt strength (such as low-melt-index LDPE) tend to break under stretching. Mixing 10%–20% LLDPE or metallocene PE can improve overall melt strength.

If regrind material is used, strictly limit its proportion (≤30% recommended) and pre-screen to remove hard contaminants like plastic impurities and metal scraps. Hard contaminants create stress concentration points on film, causing easy rupture under tension.

Besides, slightly hygroscopic materials such as HDPE will generate tiny bubbles during plasticization if damp, greatly reducing film tensile strength. Dry them with hot air at 80–100℃ for 2–4 hours in advance to fully remove moisture.

2. Equipment: Inspect key components and stabilize operation

Equipment malfunctions are major triggers of frequent film breakage. Focus on three core assemblies:

Die system: Uneven die heating or internal material buildup disturbs melt flow. Film thickness deviation over 50% leads to concentrated stress and breakage. Stop production to clean residual deposits in die dead zones every 200–300 operating hours, calibrate heating bands, and keep die temperature deviation within ±5℃.

Air ring and air chamber: Uneven airflow or clogged holes in the air ring cause non-uniform bubble cooling. Excessive bubble swing triggers abrupt transverse stress change and film rupture. Regularly clean air ring ducts, adjust air ring gap to uniform tolerance (≤0.2 mm), and stabilize air chamber pressure at 0.02–0.05 MPa to keep the bubble vertical and steady.

Haul-off system: Mismatch between haul-off speed and extrusion speed is a common issue. When haul-off speed exceeds extrusion speed by more than 5%, over-longitudinal stretching easily causes breakage. Clean haul-off roll surfaces daily to avoid residual PE sticking and forming fracture points.

3. Process Parameters: Optimize matching and balance film strength

Process parameters shall match materials and product requirements. Key adjustments:

Temperature control: Set barrel temperature at 150–180℃ and die temperature at 170–190℃. Too low temperature results in poor melt plasticization; excessive temperature triggers molecular chain degradation and reduced melt strength.

Blow-up ratio & draw ratio: Keep blow-up ratio at 2–3 (not exceeding 3), draw ratio at 4–6. Imbalance between them causes over-stretching in transverse or machine direction and insufficient film strength.

Airflow control: Adjust air ring airflow so the cooled & set bubble has no obvious swing. Excessive airflow leads to local rapid chilling and brittleness, forming weak stress zones.

4. Environment & Operation: Standardize details and reduce fluctuations

Minor variations in workshop environment and operation practices may also induce film breakage. In northern winters, if workshop temperature drops below 15℃, the bubble gets locally brittle due to rapid cooling after exiting the die. Maintain workshop temperature around 20℃. Install dust covers around bubbles for dusty workshops to prevent dust from forming stress points on film.

Avoid sudden speed increase/decrease during operation. Clean residual die material upon shutdown to prevent flow blockage and film breakage at next startup.

In summary, troubleshoot PE film breakage systematically in sequence: material → equipment → process → environment. Periodic routine maintenance (cleaning, calibration) is critical to reduce breakage frequency. Standardized control can lower film breakage rate below 1%, greatly boosting production efficiency.