Analysis of the working principle and main components of the blown film machine

Film blowing machine is a kind of equipment commonly used in the plastic processing industry, widely used in packaging, agriculture, food and many other fields. It features high efficiency and energy saving by extruding plastic raw materials and blowing them into films. The working principle of a blown film machine is complex and involves a number of processes, including extrusion, blowing, cooling and other processes. Understanding the working principle of the film blowing machine and its main components is important for improving production efficiency and product quality.

The working principle of blown film machine and its details

Blown film machines process plastic granules into film through two processes: extrusion and blow moulding. This process can be divided into several key steps:

1. Raw material heating and extrusion: The blown film machine first heats and melts the plastic granules (e.g. polyethylene, polypropylene, etc.) through the extruder. Inside the extruder is a screw, which pushes the plastic granules from the hopper to the heating zone by rotating them. In this process, the plastic pellets are heated to a sufficient melting temperature to make a more fluid melt.

2. Die head and blow moulding: The molten plastic is extruded through a die head (usually a circular die head) to form a film tubular structure. At this point, the air ring device of the film blowing machine starts working, injecting air into the tubular film and blowing the film to a predetermined thickness. At this time, the temperature of the outer wall of the film gradually cools down, but the inner wall is still at a high temperature.

3. Cooling and traction: The cooling system plays a vital role in the blown film process. The film is rapidly cooled by cold air in the cooling tower to form a stable structure. As it cools, the film cures and the traction rollers begin to pull the film to ensure uniform tension. The cooled film gradually becomes thicker, stronger and stabilises its physical properties.

4. Winding and finished output: After cooling, the film is wound into rolls by the haul-off unit. These rolled films can be cut into specified sizes as required to enter the packaging or further processing process.

The main components and functions of a blown film machine
The blown film machine is a relatively complex construction consisting of the following key components, each of which has a direct impact on the quality and efficiency of the final film:

1. Extruder: This is the heart of the blown film machine and consists mainly of the hopper, screw, heating zone and die head. The extruder pushes the plastic granules through the screw to the heating zone where they are heated and melted, and then extruded through the die head to form the tubular film. The speed of the screw, the control of the temperature, and the fluidity of the melt all have a direct effect on the uniformity and quality of the film.

2. Air ring and die head: The air ring device is responsible for blowing air evenly to expand the inner wall of the film. The design of the die head is crucial as it affects the flow of the melt and the thickness distribution of the film. Modern die heads are often designed with multi-layer runners to ensure a more uniform melt flow and reduce film thickness fluctuations.

3. Cooling towers: Cooling towers are used to rapidly reduce the film temperature through air cooling to avoid film shrinkage or deformation. The fan and air ducts in the cooling tower must be designed to ensure uniform cooling of the film surface. The performance of the cooling tower directly affects the transparency, smoothness and strength of the film.

4. Traction devices and winding systems: Traction devices help control the tension of the film to avoid uneven stretching or breakage. The take-up system is responsible for rolling the film into rolls, a process that requires a constant tension to avoid wrinkles or distortions.

Classification and characteristics of blown film machinesBlown film machines can be classified into single-layer, multi-layer and speciality blown film machines according to demand. Different types of blown film machines have significant differences in the number of layers of film produced, their functionality and suitability:

1. Single-layer blown film machine: It is suitable for the production of single material film, usually used for simple packaging needs, such as general food packaging, daily-use product packaging. Single-layer film has the characteristics of simple production process and lower cost, but the functionality is relatively single.

2. Double-layer blown film machine: double-layer blown film machine can produce two layers of different materials, commonly used in packaging that requires different functional layers, such as moisture-proof layer, UV layer. Through the double-layer structure, the physical properties and protective properties of the film can be improved, such as food packaging can be both fresh and moisture-proof function.

3. Three-layer blown film machine: Three-layer blown film machine is suitable for the production of multifunctional composite film, which is widely used in high-end packaging needs, such as food packaging, pharmaceutical packaging, etc.. The three-layer film can realise the hierarchical composite of different materials, and the function of each layer of material can be selected according to the actual needs (e.g. high temperature resistance, UV resistance, barrier property, etc.).

4. Multi-layer co-extruded blown film machine: this kind of blown film machine can not only produce three-layer film, but even five-layer, seven-layer or even more layers of film, which is commonly used in the field of packaging with special requirements, to meet the high requirements for different physical and chemical properties. For example, oil-resistant, waterproof, non-toxic and other functional films.

Application areas of blown film machines
Blown film machines are widely used in several industries, the following are some of the main areas:

1. Packaging industry: blown film machines are widely used in food packaging, pharmaceutical packaging, packaging of daily-use chemical products and so on. For example, food packaging film can ensure the freshness of food, moisture-proof, blocking external gases, anti-ultraviolet and other functions.

2. Agricultural film: In the field of agriculture, the film produced by film blowing machine is used for greenhouse greenhouse covering, mulch covering, etc., which helps to regulate the temperature, humidity, and effectively prevent pests and diseases. The special requirements of agricultural films include light transmittance, UV resistance and air permeability.

3. Electronic industry: in the packaging of electronic products, especially for the protection of precision electronic components, film blowing machine also has an important role. For example, the production of special films for battery wrapping, isolation and protection of electronic components.

4. Pharmaceutical industry: pharmaceutical packaging materials are also often made of highly functional blown film, such as pharmaceutical packaging film with barrier properties to prevent air, light on the impact of drugs.

5. Environmentally friendly materials: with the improvement of environmental awareness, blown film machines are also beginning to be used for the production of some biodegradable films, which are used to replace traditional plastic packaging and reduce plastic pollution.

The future trend of film blowing machine
With the improvement of environmental protection requirements and the development of technology, film blowing machines are also being improved and upgraded. Future trends include:

1. Intelligent control: modern film blowing machines are developing towards intelligence, through advanced sensors, data analysis and automatic control systems, to achieve precise regulation and control of film thickness, temperature, pressure, etc., to further improve production efficiency and film quality.

2. Use of environmentally friendly and biodegradable materials: With the global concern over plastic pollution, more and more blown film machines will produce films with biodegradable or environmentally friendly materials, such as PLA (polylactic acid) and other bio-based plastic films.

3. High-performance multi-layer films: with technological advances, future blown film machines may produce more layers of highly functional films, such as films with multiple protection functions, intelligent sensing functions and other special purposes, to adapt to more complex application scenarios.

Through continuous innovation and optimisation, Film Blowing Machine technology will continue to meet the growing demand for film in all industries, and make new breakthroughs in environmental protection and efficient production.