What is the 7-layer Blown Film Extrusion Line?


As experts in the field of blown film extrusion machines, we understand the importance of finding the right equipment for your manufacturing needs. In this article, we will discuss the 7-layer blown film extrusion machine and why it is an excellent choice for producing high-quality films. Our goal is to provide you with detailed information, including what the 7-layer blown film extrusion line is, how it works, and its applications that can help you make an informed decision when it comes to choosing the right machine for your business.


The 7-layer blown film extrusion line is a machine used to manufacture multi-layer films of different materials and thicknesses. The term "blown" refers to the process of extrusion, where molten plastic is forced through a circular die, and then inflated like a balloon to form a thin film. The 7-layer blown film extrusion line is capable of producing 7 layers of plastic films, each layer providing specific properties and functionalities to the final product, such as gas barrier, water vapor barrier, UV resistance, or mechanical strength. These films are used in a wide range of applications such as food packaging, medical packaging, industrial wrapping, and agricultural films.

Components of 7-layer Blown Film Extrusion Line

The typical configuration of a 7-layer blown film extrusion line consists of several of the following components that work together to produce the multi-layer film:

  1. Extruders: The extruders are the heart of the blown film extrusion line, responsible for melting and mixing the plastic resins. In a 7-layer configuration, there are typically 7 extruders, each dedicated to a specific resin.
  2. Feedblock: The feedblock is a critical component of the co-extrusion die, which controls the distribution and layer thickness of the different resins. It ensures that the layers are evenly distributed and that the film has the desired properties.
  3. Co-extrusion die: The co-extrusion die is responsible for combining the molten resins into a multi-layered structure. It is designed to achieve precise control over the thickness and distribution of each layer.
  4. Bubble cage: The bubble cage is a cylindrical structure that supports the blown film as it is inflated. It ensures that the film is evenly expanded and that it has the desired thickness and width.
  5. Cooling system: The cooling system consists of a series of fans and cooling rollers that rapidly cool the film after it exits the bubble cage. This process is critical to ensure that the film maintains its desired properties and does not deform or shrink.
  6. Winding system: The winding system is responsible for winding the film onto a roll, which can be easily transported and used for downstream processes such as printing, laminating, or bag-making.
  7. Control system: The control system is responsible for monitoring and controlling the various components of the blown film extrusion line. It ensures that the process parameters such as temperature, pressure, and speed are maintained within the desired ranges to ensure consistent and high-quality film production.

How does it Work?

7-layer blown film extrusion lines consist of multiple extruders, each of which is used to melt and mix a specific type of plastic resin. The melted resins are then fed into a co-extrusion die, where they are combined into a multi-layered structure before being blown into a tube and flattened into a film.

  1. The first step by extruders is to melt the plastic pellets and pumps the molten plastic through a circular die. The die creates a tube of plastic that is cooled with air or water as it travels through the extrusion line. The tube is then inflated, and air pressure is applied to stretch and thin out the film.
  2. The second step by the multi-layer feedblock, which divides the molten plastic into multiple layers and combines them into a single film. The feedblock controls the layer thickness, and the different layers are then stacked on top of each other to form the 7-layer films.
  3. After the feedblock co-extrusion, the film passes through a series of cooling rollers, which cool and solidify the plastic film. The film is then wound onto a roll or cut into smaller sections for further processing into the final product.

(Further reading: What is the Manufacturing Process of Blown Film Extrusion?)

Advantages of 7-layer Blown Film Extrusion Line

The advantages of using a 7-layer blown film extrusion line include:

  • Improved barrier properties: The use of multiple layers of different materials allows for precise control over the barrier properties of the film, including oxygen, water vapor, and light. This is critical for applications such as food and medical packaging, where the film must protect the contents from contamination or degradation.
  • Enhanced mechanical properties: The use of multiple layers also allows for enhanced mechanical properties such as puncture resistance, tear resistance, and tensile strength. This is important for applications such as industrial wrapping, where the film must withstand heavy loads and rough handling.
  • Reduced material costs: The use of multiple layers can also allow for the use of lower-cost materials in some layers while maintaining the desired properties. This can help to reduce material costs and improve profitability.
  • Improved processing efficiency: The use of a co-extrusion die and multi-layered structure also allows for improved processing efficiency, reducing waste and improving productivity.

Applications of 7-layer Blown Film Extrusion Line

The multi-layer film produced by the extrusion line provides various properties, such as high barrier properties, puncture resistance, and sealability, that are used in various industries, including food packaging, medical packaging, and industrial packaging:

  • Food packaging industry: In the food packaging industry, the 7-layer blown film extrusion line is used to produce packaging materials that protect food from oxygen, moisture, and other contaminants. The multi-layer film also provides a longer shelf life for perishable foods, such as meat, cheese, vegetables, and snack foods.
  • Medical packaging industry: In the medical packaging industry, the 7-layer blown film extrusion line is used to produce sterile packaging materials for medical devices and pharmaceuticals. The multi-layer film provides a high barrier to oxygen and other contaminants, ensuring the product remains sterile.
  • Industrial packaging industry: In the industrial packaging industry, the 7-layer blown film extrusion line is used to produce heavy-duty packaging materials that can withstand harsh environments and rough handling. The multi-layer film provides excellent puncture resistance, tear strength, and durability.

(Further reading: 5/7/9 Blown Film Extrusion Lines for Barrier Film : The Ideal Choice for Food Packaging)


In conclusion, the 7-layer blown film extrusion machine is an excellent choice for producing high-quality films with excellent barrier properties. It is commonly used such as food packaging, medical packaging, industrial wrapping, and the agricultural industry. and offers several advantages over other types of film extrusion machines. When choosing the right machine, it is important to consider the materials that will be used and the production capacity of the machine to ensure that it meets your specific manufacturing needs.

If you have any blown film extrusion machine needs or questions, welcome to contact us!

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