Plastic film is everywhere in modern life, and the key to its production lies in the film blowing machine. This article will analyze the film blowing machine in depth, covering the principle, structure, application and other aspects, to help you fully understand this important plastic processing equipment.
I. Introduction
In the modern plastic processing industry, the blown film machine plays an extremely crucial role. It is the key equipment for manufacturing various plastic films and is widely applied in numerous fields like packaging, agriculture, and construction, providing technical support to meet the diverse demands of different industries for plastic films.
II. Basic Principle of the Blown Film Machine
The working principle of the blown film machine is based on the extrusion and blown film forming processes of polymers. The details are as follows:
1. Plasticizing of Raw Materials
Firstly, raw materials such as plastic pellets are added into the hopper of the extruder. Under the rotating action of the extruder screw, the raw materials are conveyed, compressed, melted, and plasticized to form a uniform melt.
2. Extrusion Molding
The plasticized melt is extruded through the annular die orifice of the extruder head, thus forming a tubular film blank.
3. Blowing and Traction
Simultaneously when the film blank is being extruded, compressed air is introduced into the tube to inflate the film blank into a film with the desired diameter and thickness. Meanwhile, the film is continuously pulled forward by the traction device.
4. Cooling and Setting
The inflated film is cooled by cooling devices like cooling air rings or cooling water tanks to set the film and maintain its shape and properties.
III. Main Components of the Blown Film Machine
1. Extrusion System
Extruder: It is the core component. Commonly, there are single-screw extruders and twin-screw extruders. The single-screw extruder has a simple structure and low cost and is suitable for extruding multiple types of plastic raw materials. The twin-screw extruder has better mixing and plasticizing effects and stronger adaptability to materials.
Hopper: It is used for storing and supplying plastic raw materials, and its capacity varies according to the production scale.
Screw and Barrel: Design parameters of the screw, such as diameter, length-to-diameter ratio, and screw groove depth, have a significant impact on the conveying and plasticizing efficiency of materials. The barrel provides space for the plasticizing of materials and can control the temperature of materials through heating or cooling devices.
2. Die Head and Mold
Die Head: It determines the shape and size of the film. Commonly used die heads include the mandrel die head, spiral die head, and coat hanger die head. The mandrel die head has a simple structure, but the flow uniformity of materials in the die head is slightly poorer. The spiral die head enables better mixing and uniform distribution of materials in the die head. The coat hanger die head is suitable for producing wide-width films with relatively uniform material distribution.
Die Orifice: The size of its gap can adjust the thickness of the film. It is usually made of materials like stainless steel to ensure the precision and durability of the die orifice.
3. Cooling System
Air Ring: It is the most commonly used cooling device. By blowing cold air onto the surface of the film, it enables the film to cool rapidly. The structure of the air ring and the adjustment of air volume and wind speed have an important impact on the cooling effect and quality of the film.
Cooling Water Tank: For the production of some films that require more thorough cooling or are made of special materials, a cooling water tank will be used for cooling. When the film passes through the water tank, it exchanges heat with water to achieve the purpose of cooling and setting.
4. Traction System
Traction Rolls: Composed of one or more pairs of rubber rolls or steel rolls, they pull the film forward by means of friction. The rotational speed of the traction rolls can be adjusted to control the traction speed and draw ratio of the film.
Traction Motor: It provides power for the rotation of the traction rolls, and its power is determined according to factors such as the production speed and width of the film.
5. Winding System
Winding Roll: It winds the cooled and set film into rolls. The diameter and width of the winding roll are determined according to the specifications of the film.
Tension Control System: It is used to control the tension of the film during the winding process to ensure that the film is wound tightly and smoothly, avoiding wrinkles or slack.
IV. Application Fields of the Blown Film Machine
1. Packaging Industry
Food Packaging: It is used to produce plastic wrap, storage bags, food packaging bags, etc. for food packaging, which can effectively prevent food from spoiling, getting damp, or being contaminated, thus extending the shelf life of food.
Daily Necessities Packaging: For example, in the packaging of cosmetics, stationery, toys, etc., it provides beautiful, lightweight packaging materials with certain protective properties.
Industrial Product Packaging: It is used to package various industrial parts, electronic products, etc., playing roles in protection, dust prevention, and moisture prevention, facilitating the transportation and storage of products.
2. Agricultural Field
Agricultural Films: Including plastic greenhouse films, mulching films, etc. Greenhouse films can be used for the cultivation of crops such as vegetables, flowers, and fruits, playing roles in heat preservation, moisture retention, wind prevention, and rain prevention, improving the growth environment of crops and increasing yield and quality. Mulching films can suppress the growth of weeds, maintain soil moisture and temperature, and promote the early maturity of crops.
3. Construction Industry
Waterproofing Membranes: The blown film machine can produce waterproofing membranes for waterproofing projects such as building roofs and basements, such as polyethylene-polypropylene waterproofing membranes, which have good waterproof performance and durability.
Insulation Materials: It is used to produce building insulation films and other products, which can effectively block the heat of solar radiation from entering buildings, reduce the energy consumption of buildings, and improve the indoor comfort level.
V. Technological Development Trends of the Blown Film Machine
1. Intelligent Control
Advanced automatic control systems are adopted to achieve precise control and real-time monitoring of various technological parameters of the blown film machine, such as temperature, pressure, and speed, improving the production efficiency and the stability of product quality. Meanwhile, it has functions of fault diagnosis and early warning, reducing equipment downtime and maintenance costs.
2. Energy Saving and Consumption Reduction
Measures such as optimizing the screw design of the extruder and improving the heating and cooling systems are taken to reduce the energy consumption of the blown film machine. For example, new energy-saving motors, high-efficiency heating elements, and thermal insulation materials are used to improve energy utilization efficiency.
3. Multi-layer Co-extrusion Technology
Multi-layer co-extrusion blown film machines are developed to produce multi-layer composite films with different properties. For example, in the packaging field, by combining barrier layers, functional layers, and base layers, the barrier performance, preservation performance, and puncture resistance of films can be improved to meet the needs of high-end packaging.
4. Application of Green and Environmentally Friendly Materials
With the enhancement of environmental awareness, the blown film machine is gradually adapting to the processing of green and environmentally friendly materials such as degradable plastics. For example, films are produced by using degradable materials like polylactic acid (PLA) and starch-based plastics, reducing the dependence on traditional petroleum-based plastics and minimizing the pollution of plastic films to the environment.
VI. Conclusion
As the key equipment for producing plastic films, the blown film machine's principle, components, and applications cover multiple aspects of technology and knowledge. With the continuous progress of science and technology and the changes in market demands, the blown film machine will continue to develop in aspects such as intelligence, energy saving, multi-functionality, and environmental protection, bringing more innovation and development opportunities to the plastic processing industry and related application fields, and promoting continuous improvement in the quality, performance, and environmental protection of plastic film products to better serve various industries in modern society and people's daily lives.
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