What are the advantages and disadvantages of extrusion blown film machines?

Plastic film extrusion is one of the most important processes in the shipping and product manufacturing industries. It produces 25% of all thermoplastics used in the industry, especially food and daily packaging, while the rest of the extruded film is used in construction and agricultural machinery.

During the plastic film extrusion process, the molten polymer is pushed through a circular die. The process is repeated regularly and produces high-quality products of the same quality and precise specifications. The production of very thin specification films involves blown film extrusion or cast film extrusion.

Extrusion blown film, in addition to producing very thin films, involves extruding a tube of molten polymer through a die head and expanding it multiple times to produce film bubbles. The bubbles are then molded into different shapes. A variety of types of polymers can be used in this process. The most common method of film extrusion is vertically upward.

Recently, lateral and downward variations of extrusion have also become popular in the industry. The four most common steps of film extrusion are: Initially, the polymer polyethylene is in pellet form, which is melted and compacted with the help of heavy machinery to convert the pellets into a viscous liquid, and then the liquid is passed through a circular die. Next, air is also inserted through the hole present in the center of the annular die, and the pressure turns the extruded material into bubbles. Uniform pressure is maintained throughout the process to ensure uniform thickness of the film. The newly formed bubbles are constantly pulled upwards and air is blown into the film. As a result, the film cools from the inside and the internal temperature drops sharply. The product solidifies and the film is produced by the rollers, which complete the bubbles and compress them into a flat film layer. The film passes through different rollers such as wind-up rollers, idler rollers and nip rollers to ensure uniform thickness of the film. Finally, the film can be formed into different shapes and products for different industries.

Advantages of Extrusion Blown Film

Extrusion blown film machines are more balanced in mechanical properties than simple or extruded films because it passes through various machines and transverse directions. Stretch film manufacturers also ensure that the produced film is stretchable, flexible and strong. A large film, two smaller films or films of other shapes can be produced by blown film extrusion. There is no need for excessive trimming after the film is made, and a single die can be used to make films of different shapes and sizes. Blown film extrusion requires a lower melt temperature than cast extrusion. It reduces manufacturing costs.

Disadvantages of blown film extrusion

The cooling process of blown film is an inefficient process compared to flat film. Flat film is cooled by water or cooling rollers, which have a greater heating capacity than the air used in blown film extrusion. It is difficult to accurately control the thickness of blown film. The process is rather complex and there are many factors that can go wrong. Due to the complex production method, cast film can be produced at a much higher speed than blown film. Both types of stretch film are commonly used. During film extrusion, the danger of air being entrapped between the film layers and the rollers is serious, which can interfere with the entire manufacturing process. It causes the newly produced film to wrinkle or scratch, so it eventually has to be discarded or reused in another way. A vacuum cleaner is usually installed to avoid air entrapment.