In the current era where plastic films are widely used, the blown film machine, as the core equipment for producing plastic films, has a variety of types that offer multiple options to meet different production needs. Different types of blown film machines show significant differences in several key aspects, which profoundly affect the production process and the final product quality of plastic films.
I. Differences in Extruder Types
The extruder is the heart of the blown film machine, and different types of extruders endow the blown film machine with different performance characteristics.
The single-screw blown film machine is widely known for its simple structure. Its design is relatively straightforward, and its manufacturing and maintenance costs are also relatively low. This type of blown film machine performs stably in processing common plastic raw materials and can handle the extrusion and film forming tasks of general plastic pellets such as polyethylene (PE) and polypropylene (PP). It is suitable for some production scenarios where the requirements for film performance are not extremely stringent, for example, in the production of ordinary shopping bags and simple packaging films. However, due to its single-screw design, it is somewhat insufficient when dealing with some raw materials with complex formulations or requiring a high degree of mixing and plasticizing effects.
In contrast, the twin-screw blown film machine has excellent performance in material mixing and plasticizing. It can efficiently mix, shear, and plasticize multiple raw materials with different characteristics simultaneously. This gives it a unique advantage in the production of films with complex formulations or special performance requirements. For example, when it is necessary to produce films with high barrier properties, high strength, or special functional additives, the twin-screw blown film machine can accurately and thoroughly mix different resins, additives, and other raw materials to ensure the consistency and stability of the performance of the final film product. However, this high performance comes with higher equipment costs and relatively complex maintenance requirements, and it requires more professional technicians for operation and maintenance.
II. Differences in Die Head Structures
The die head structure is a key factor that determines the shape, size, and quality uniformity of the films produced by the bThe die head structure is a key factor that determines the shape, size, and quality uniformity of the films produced by the blown film machine.
The blown film machine with a mandrel die head has a relatively simple structure. Its working principle is based on the material flowing around the mandrel and being extruded and formed. This die head structure makes the overall cost of the equipment relatively low and is widely used in some small plastic processing enterprises or production scenarios where the requirements for film quality are not too high. However, due to its relatively single material flow path, it is difficult to achieve a very high level of flow uniformity of materials in the die head. As a result, the films produced by the blown film machine with a mandrel die head may have certain deviations in thickness uniformity. Especially when producing small and medium-sized films with relatively strict requirements for thickness accuracy, this limitation becomes more obvious. For example, when producing small packaging films for stationery or simple food cling films, if the requirements for thickness uniformity are not high, the blown film machine with a mandrel die head can meet the basic production needs, but it is difficult to achieve high-precision control of film thickness.
The blown film machine with a spiral die head performs outstandingly in material mixing and uniform distribution. Its unique internal spiral structure can guide the materials to flow and mix in multiple directions in the die head, enabling the materials to be evenly distributed throughout the entire die head flow channel. This characteristic of uniform distribution greatly improves the stability of film quality, making the produced films more uniform in optical properties such as transparency and gloss, and also more consistent in physical properties such as tensile strength and tear resistance. Therefore, the blown film machine with a spiral die head is suitable for production scenarios where there are certain standards for the optical and physical properties of films, such as the production of high-quality food packaging films and electronic packaging films. These products require films to have good appearance quality and stable physical properties to ensure the safety and quality of the packaged contents.
The blown film machine with a coat hanger die head occupies an important position in the field of wide-width film production. Its unique coat hanger-shaped flow channel design can ensure that materials are evenly spread and distributed over a large width. When producing large packaging films, such as large outer packaging films for industrial products and agricultural greenhouse films, the blown film machine with a coat hanger die head shows incomparable advantages. It can effectively avoid problems such as uneven material distribution and excessive differences in film thickness caused by excessive width, ensuring the quality stability of wide-width films across the entire width range. However, this die head structure is relatively complex, with high design and manufacturing costs, and requires more precise adjustment of production process parameters. Operators need to have rich experience and professional knowledge.
III. Differences in Cooling Methods
The cooling method also has a crucial impact on the efficiency and quality of films produced by the blown film machine.
The blown film machine with an air ring cooling system is the most common type. Its working principle is to achieve cooling and setting by blowing cold air onto the surface of the film that has just been extruded and inflated. This cooling method has a moderate cooling efficiency and can meet the cooling requirements of most conventional films. In actual production, operators can flexibly control the cooling effect of the film by adjusting parameters such as the air volume, wind speed of the air ring, and the distance between the air ring and the film. For example, when producing ordinary-thickness polyethylene films, air ring cooling can effectively cool and set the films quickly, ensuring the dimensional stability and surface flatness of the films. Moreover, the air ring cooling equipment has a relatively simple structure, low cost, and is relatively convenient for operation and maintenance. Therefore, it is widely used in many small and medium-sized plastic film production enterprises.
The blown film machine with a cooling water tank adopts a completely different cooling method. It takes advantage of the high specific heat capacity of water to allow the film to exchange heat fully with water when passing through the water tank, thus achieving a rapid and powerful cooling effect. This cooling method is particularly suitable for the production of thick-walled films or films with special requirements for thermal stability. Thick-walled films have a relatively large thickness, and heat dissipation is relatively slow. If air ring cooling is used, it may lead to uneven cooling or a long cooling time, which will then affect the performance and production efficiency of the films. The cooling water tank can quickly take away the heat inside the thick-walled films and set them quickly to ensure the quality of the films. However, the blown film machine with a cooling water tank has a relatively complex equipment equipment structure and needs to be equipped with a special water circulation system, water treatment equipment, and film drying device. Meanwhile, since the film is in direct contact with water, there are higher requirements for the cleaning treatment of the film surface to prevent impurities in the water from contaminating the film surface and affecting the appearance and performance of the films.
In conclusion, different types of blown film machines have obvious differences in aspects such as the range of applicable raw materials, film quality control, production efficiency, and equipment cost and maintenance difficulty. For plastic film production enterprises, it is crucial to have an in-depth understanding of these differences and carefully select the appropriate type of blown film machine according to factors such as their own product positioning, production scale, and budget. Only by choosing the blown film machine that best matches their production needs can enterprises win the trust of customers with high-quality film products and achieve sustainable development in the fierce market competition.
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