What are the differences in structural composition among different types of Dalian blown film units?

The blown film unit, as the core technology equipment for plastic film production, plays an important role in modern industry. Its high efficiency, flexibility, and low cost make it the preferred equipment for the plastic processing industry. With the continuous advancement of technology and the diversification of market demand, blown film units will continue to develop towards high efficiency, energy saving, intelligence, and environmental protection, providing better technical support for the production and application of plastic films.

The extruder is the heart part of the blown film unit, responsible for heating, melting, and extruding plastic particles. Extruders are usually composed of screws, barrels, heaters, and driving devices. The design and speed of the screw directly affect the melting effect and extrusion volume of the plastic. The die head is a key component for forming a thin film of plastic melt after it exits the extruder. The design of the die determines the thickness, width, and uniformity of the film. The common types of die heads include circular die heads and flat die heads.

What are the differences in structural composition among different types of Dalian blown film units?

The differences in the structural composition of different types of blown film units are mainly reflected in the extrusion system, die head, cooling system, traction system, etc. The following is a specific introduction:

Extrusion System

Single screw blown film unit: usually uses a single screw extruder with a relatively simple structure, consisting of a screw and a material cylinder. The diameter and aspect ratio of the screw vary according to production requirements, generally ranging from 20-30. This extruder is suitable for processing conventional plastic raw materials such as polyethylene (PE), polypropylene (PP), etc. The plastic raw materials are transported from the hopper to the front end of the barrel through the rotation of the screw, and gradually melted and extruded under the heating and shearing action of the screw.

Twin screw blown film unit: equipped with a twin screw extruder, with two interlocking screws. The conveying capacity and mixing plasticization effect of twin-screw extruder are better, which can handle high filling and high viscosity plastic raw materials, as well as modify and process plastics. Its screw structure is relatively complex, with various thread combinations and component configurations that can be adjusted according to different process requirements. The interaction between the two screws causes stronger shear and mixing of the plastic during extrusion, which can better ensure the uniformity and stability of the plastic melt.

Die head

Upward blowing method film blowing unit: The mold head is usually an upward structure, and the discharge port is in a horizontal circular shape. This die design facilitates the upward inflation of the extruded tubular film, which is beneficial for the film to naturally sag under the action of gravity, allowing the film to be uniformly stretched and shaped during the cooling process. At the same time, the size of the blow up method die is relatively large, which can meet the needs of producing wide width films. It is generally used for producing films with a width of 2-10 meters or even wider.

Downward blowing method film blowing unit: The mold head is facing downwards, and the discharge port is also circular. The advantage of the down blowing method for mold heads is that it is easy to install and operate, especially for producing ultra-thin films. The down blowing method can better control the thickness uniformity of the film. Because the gravity acting on the film during the downward inflation process is consistent with the direction of the inflation force, it is beneficial for the stable molding of the film. In addition, the blow down mold head is usually equipped with special cooling devices, such as cooling water tanks or a cooling system combining air and water cooling, to quickly cool the film, improve production efficiency and film quality.

Flat blowing method film blowing unit: The mold head is in a horizontal direction, and the discharge port is in the shape of a flat slit or ring. The flat blowing method has a simple mold head structure, occupies a small area, and is suitable for producing small and medium-sized films. However, due to the horizontal expansion of the film and uneven cooling, it is prone to uneven film thickness. In order to improve this problem, the flat blowing die head is usually specially designed in terms of cooling and traction systems, such as using multiple cooling nozzles to evenly cool the film, and controlling the stretching and thickness distribution of the film by adjusting the speed and pressure of the traction rollers.

Cooling system

Upward blowing method film blowing unit: usually adopts air cooling method, and the cooling air ring is located above the mold head. The cold air blown out by the cooling air ring is evenly blown towards the surface of the film, causing the film to rapidly cool and solidify during the upward expansion process. In order to ensure the cooling effect, the structural design of the cooling air ring is crucial. Generally, special air duct designs and outlet shapes are used to ensure that the blown air is uniform and stable, and can be adjusted according to the thickness and production speed of the film. In addition, some large top blown film blowing units are also equipped with auxiliary cooling devices, such as setting cooling rollers or cooling plates during the film traction process, further reducing the temperature of the film and improving its quality and performance.

Downward blowing method film blowing unit: often adopts a cooling method of water cooling or a combination of air cooling and water cooling. Water cooling systems usually consist of a cooling water tank and a circulating water system. After the film is blown out of the mold head, it directly enters the cooling water tank for cooling. This cooling method can quickly and effectively reduce the temperature of the film, allowing it to quickly solidify, making it particularly suitable for producing ultra-thin films. The air-cooled part is mainly used to dry and further cool the surface of the film, preventing the formation of water droplets or condensed water vapor on the surface of the film. The combination of air cooling and water cooling can fully utilize the advantages of both cooling methods, improve the cooling effect and film quality.

Flat blowing method film blowing unit: generally adopts air cooling method, with cooling nozzles distributed on both sides of the film. Due to the horizontal expansion of the flat blowing method film, the position and angle of the cooling nozzle have a significant impact on the cooling effect. In order to achieve uniform cooling of the film, the cooling nozzles are usually arranged reasonably according to the width and thickness of the film, and the cooling speed can be controlled by adjusting the air volume and speed of the nozzles. In addition, some flat blowing film blowing units also add air heating devices to the cooling system to preheat the cooling air during the production process, preventing the film from developing internal stress or cracking due to rapid cooling.

traction system

Upward blowing method film blowing unit: The traction system usually consists of multiple sets of traction rollers located above the film. Due to the upward expansion and natural sagging of the blown film, the traction roller needs to have sufficient traction and stability to overcome the gravity and tension of the film and smoothly pull it to the winding device. The surface of the traction roller is usually made of special materials and processed to increase the friction with the film and prevent the film from slipping during the traction process. At the same time, the traction system will also be equipped with a tension control system, which precisely controls the tension of the film by adjusting the speed and pressure of the traction roller, ensuring the flatness and thickness uniformity of the film.

Bottom blowing method film blowing unit: The traction system is located below the film, and its structure and principle are similar to the top blowing method, but with some differences in details. Due to the gravitational force acting on the film during the downward expansion process, the traction system needs to pay more attention to supporting and guiding the film to prevent it from shaking or deforming during the traction process. Therefore, the traction rollers of the down blowing traction system usually use more precise bearings and transmission devices to improve the accuracy and stability of traction. In addition, the tension control system of the downward blowing traction system also needs to be optimized according to the characteristics of the film to adapt to the tension changes of the film during the downward traction process.

Flat blowing method film blowing unit: The traction system is relatively simple, generally consisting of one or more pairs of traction rollers located on both sides of the film. The flat blowing method blows the film horizontally, and the traction roller is mainly used to pull the film from the die to the winding device, and control the traction speed and tension of the film. Due to the relatively small width of the flat blown film, the load on the traction system is relatively light, but there are high requirements for the flatness and tension control in the width direction of the film. Therefore, the flat blowing traction system is usually equipped with a high-precision width control system and tension adjustment device to ensure that the film maintains good flatness and width stability during the traction process.

The blown film unit is a mechanical equipment used for producing plastic film, widely used in packaging, agriculture, construction, medical and other fields. The blown film unit heats and melts plastic particles, and then produces thin films through blow molding. This type of film has the characteristics of high transparency, good strength, and excellent flexibility, which can meet the needs of different industries.

The blown film unit is used for producing food bags, cling film, vacuum packaging film, etc., and has good barrier performance and hygiene safety. Used for producing plastic film, greenhouse film, etc., it has functions such as insulation, moisture retention, insect prevention, etc., which can increase crop yield. Used for producing industrial films, wrapping films, protective films, etc., it has the characteristics of high strength and wear resistance.