Dalian Blown Film Unit: Core Equipment for Plastic Film Forming

Dalian Blown Film Unit: Core Equipment for Plastic Film Forming

A blown film unit is a complete set of core equipment for producing plastic films in the plastics processing industry, widely used in packaging, agriculture, industry and other fields. Its products cover daily consumer goods packaging, agricultural thermal covering, industrial protection and many other applications, making it one of the vital devices supporting the development of the modern light industry.

A complete blown film unit mainly consists of six core modules: extrusion system, die head system, cooling and shaping system, haul-off conveying system, winding system and electrical control system. The extrusion system serves to plasticize raw materials. With the cooperation of screw and barrel, solid plastic materials such as polyethylene (PE) and polypropylene (PP) are heated, sheared and mixed, turning from solid state into homogeneous molten fluid. The annular die head system is critical to film forming quality, and the precision of die gap directly affects film thickness uniformity. Composed of air ring and cooling fan, the cooling system quickly shapes the film bubble to prevent deviations caused by uneven temperature. The haul-off system adjusts the film width via haul-off speed matched with blow-up ratio by multiple sets of haul-off rollers. The winding system rolls continuous film into finished rolls. The electrical control system mostly adopts PLC to realize precise control of temperature, pressure and speed, ensuring stable automatic production.

The working principle of blown film units lies in plastic melting, extrusion, blowing and shaping. Raw materials are fed into the extrusion system through hopper. After plasticization, molten materials extrude through the gap of the annular die head to form a tubular film parison. Compressed air is introduced from the center of the die head to inflate the parison into a film bubble of specified diameter, known as blowing-up. The air ring rapidly cools and shapes the outer surface of the bubble to avoid collapse and deformation. The shaped film bubble is flattened and stretched by haul-off rollers, and finally wound by the winding system. Precise coordination of blow-up ratio, haul-off speed and cooling wind speed is the key to manufacturing films with uniform thickness and stable quality.

Blown film units are categorized by functions and structures. Classified by raw materials, PE blown film units are widely adopted due to broad adaptability and low cost, while PP and PVC blown film units are applied for specific scenarios. In terms of hauling direction, there are upward-blowing, downward-blowing and horizontal-blowing types. The downward-blowing process is suitable for large agricultural greenhouse films. Co-extrusion blown film units belong to high-end equipment, which can extrude multi-layer different materials to produce barrier and fresh-keeping composite films extensively used in food and medical packaging.

They are applied across numerous sectors of the national economy: express bags, food packaging bags and daily plastic films in the packaging industry are mostly produced by such equipment; agricultural mulch films and greenhouse films manufactured by blown film units feature heat preservation, soil moisture retention and pest resistance, supporting agricultural yield increase; geomembranes and waterproof sheets in the industrial field usually adopt the blown film process to meet engineering protection requirements.

With technological advances and stricter environmental standards, Dalian blown film units are developing toward intelligence, high efficiency and environmental friendliness. On-line thickness detection and automatic adjustment systems modify die gaps in real time to reduce defective rates. Servo drive systems replace traditional motors to cut energy consumption by 10%–15%. Special units compatible with degradable materials (PLA, PBAT) are gaining popularity to meet green transformation demands. In the future, blown film units will further integrate intelligent manufacturing technology, supply eco-friendly high-performance film products for various industries, and promote high-quality development of the plastics processing sector.