Advanced Shrink Film Manufacturing Line: Orientation Control and Shrink Force Optimization 2026
A shrink film manufacturing line produces films that shrink uniformly when heated, tightly conforming to the product. The film is typically made from LDPE, LLDPE, or blends, with high clarity and low haze. The key process is controlling the orientation (MD and TD) to achieve the desired shrink percentage and force. The MD orientation is controlled by the draw-down ratio (DDR), which is the ratio of haul-off speed to melt exit speed. The TD orientation is controlled by the BUR. The product of DDR and BUR (the orientation factor) determines the total orientation. For balanced shrink, the MD and TD shrink should be similar; this is achieved when the orientation factor is around 10-15, and the DDR/BUR ratio is balanced. The line speed is moderate (80-150 m/min), and the film thickness is 15-40 µm. The cooling system is designed to freeze the orientation; rapid cooling is used to lock in the orientation, which increases shrink force. The frost line is kept low to freeze orientation quickly. The die is often oscillating to average out gauge bands. The winder must maintain consistent tension to avoid premature shrink. In summary, the shrink film line is optimized for orientation control, with precise adjustments of DDR and BUR. The shrink performance is tested by immersing the film in hot water (90-100°C) and measuring the percentage of shrink in MD and TD. The operator adjusts the haul-off speed (DDR) and internal pressure (BUR) to achieve the target shrink.
The shrink force is the tension generated during shrinkage, which affects the film's ability to tightly wrap the product. Higher shrink force provides better bundling but may deform soft products. The shrink force is influenced by the orientation and the polymer's modulus. To increase shrink force, higher orientation (higher DDR and BUR) and faster cooling are used. The film's clarity and gloss are also important; these are enhanced by rapid cooling and low haze. The use of mLLDPE in the blend improves strength and clarity. The line's AGC ensures uniform thickness, which is critical for consistent shrink. The winder must produce rolls with good lay-flat to prevent wrinkles. In practice, the shrink film line is often dedicated to a limited number of products to maintain consistent orientation. The operator must monitor the shrink test results and adjust the line speed and BUR accordingly. In conclusion, the shrink film manufacturing line is a specialized line that requires precise orientation control to produce films with the desired shrink properties for packaging applications.
Blown Film Machine
Key shrink parameters: – MD shrink: typically 30-60%. – TD shrink: typically 30-60%. – Balanced shrink: MD≈TD. – Shrink force: measured at shrinkage temperature. – Orientation factor (DDR × BUR): 10-15 for balanced. – DDR: 5-15. – BUR: 2.5-3.5. – Cooling: rapid to freeze orientation. Process control: – Haul-off speed adjusts DDR. – Internal pressure adjusts BUR. – Cooling air flow adjusts orientation freeze. – Line speed set for target thickness. – AGC for thickness uniformity. Quality tests: – Shrink percentage in hot water (90°C). – Shrink force. – Haze, gloss. – Tensile strength. In practice, the shrink film line is often run with a blend of LDPE and LLDPE to balance clarity and strength. The operator must regularly check shrink and adjust if the resin batch changes. In conclusion, orientation control is the heart of shrink film production, and the line must be equipped with precise controls to achieve the target shrink properties.
