Introduce the key technologies of three-layer co extrusion blown film machine

As an advanced plastic film production equipment, the three-layer co extrusion blown film machine achieves the production of multi-layer composite films through co extrusion technology, with excellent performance and wide application prospects. With the continuous advancement of technology and the growth of market demand, three-layer co extrusion blown film machines will play an increasingly important role in the field of plastic processing, promoting the rapid development of industries such as packaging, agriculture, and construction.

Through three-layer co extrusion technology, different performance plastic raw materials can be combined together to make the film have better comprehensive performance. For example, the outer layer can be made of materials with good glossiness and printing performance, the middle layer can be made of materials with high strength and barrier properties, and the inner layer can be made of materials with good heat sealing performance to meet the requirements of different application scenarios for film performance.

Introduce the key technologies of three-layer co extrusion blown film machine

Extrusion technology

Multi screw extrusion system: equipped with three extruders, each responsible for extruding different raw materials. The design of the screw is crucial, and it is necessary to optimize the length to diameter ratio, groove depth, compression ratio, and other parameters of the screw based on the characteristics of different plastic raw materials, such as melt index and viscosity, in order to achieve efficient plasticization and stable extrusion. For example, for high viscosity raw materials, larger aspect ratio screws may be required to increase plasticization time and shear force, allowing them to fully melt and mix.

Accurate temperature control: Each extruder has an independent heating and cooling system, which controls the temperature of each section of the barrel within a set range through high-precision temperature sensors and controllers, ensuring that plastic raw materials melt at the appropriate temperature to achieve good fluidity and plasticizing quality. The general temperature control accuracy can reach ± 1 ℃ or even higher, which is crucial for ensuring the uniformity of the film's performance.

Co extrusion composite technology

Mold head design: The mold head is the core component for achieving three-layer co extrusion composite. The internal flow channel design is complex, and it is necessary to ensure that three different plastic melts can converge and recombine uniformly in the mold head, and maintain stable flow rate and pressure distribution during the extrusion process to obtain a three-layer film with uniform thickness and strong composite. The advanced die head adopts a streamlined design to reduce dead corners and stagnant areas in the flow channel, avoiding material degradation or discoloration caused by prolonged residence time.

Melt distribution technology: Through a precise melt distribution system, the extrusion amount and flow rate of each plastic melt are accurately controlled according to the thickness requirements of each layer of the film. This requires precise adjustment and optimization of the extruder's speed, back pressure, and flow channel structure inside the die head to achieve precise control of the thickness of each layer of film. Typically, the thickness tolerance can be controlled within ± 5%.

Inflation and cooling technology

Efficient inflation system: The inflation device blows an appropriate amount of compressed air into the extruded film blank to inflate it to the desired diameter and thickness. Swelling ratio is an important process parameter that directly affects the mechanical and optical properties of thin films. Reasonably select the inflation ratio and precisely control the flow rate and pressure of the air blown in, so that the stretching degree of the film at each point is uniform and consistent during the inflation process, thereby improving the strength and transparency of the film.

Optimizing cooling technology: The cooling system plays a crucial role in the rapid shaping and quality control of thin films. Common cooling methods include a combination of air cooling and water cooling. The design of the cooling air ring is reasonable, which can provide a uniform annular airflow to quickly cool the inflated film, while ensuring uniform surface temperature of the film, preventing local overheating or undercooling, and avoiding internal stress or uneven thickness of the film. The water cooling system is used to further cool the film, improve cooling efficiency, and shorten the production cycle.

Traction and winding technology

Precision traction control: The traction device adopts high-precision motors and transmission systems, which can accurately control the traction speed of the film, match it with the extrusion speed and inflation speed, and maintain the tension stability of the film during the production process. At the same time, the tension of the film is monitored in real time through a tension sensor and fed back to the control system for automatic adjustment, ensuring that the film does not experience excessive stretching or relaxation during the traction process, and guaranteeing the dimensional stability and quality of the film.

Automatic winding technology: The winding device has functions such as automatic coil changing and constant tension winding. During the winding process, by controlling the winding speed and tension, the film is neatly wound on the reel to avoid problems such as curling, wrinkling, or loosening. When a roll of film is wound, the automatic roll changing device can quickly and accurately switch to a new roll, achieving continuous production and improving production efficiency.

Control systems technology

Automation control: Advanced programmable logic controllers (PLCs) or industrial computer control systems are used to centrally control and monitor key process parameters such as extruder speed, temperature, pressure, inflation air flow and pressure, traction speed and tension, and winding speed. Operators can easily set and adjust various parameters through the touch screen or industrial computer interface, and view the real-time operation status and production data of the equipment.

Intelligent monitoring and fault diagnosis: The control system has intelligent monitoring function, which can analyze and judge the operating status of the equipment in real time. When abnormal situations occur, such as high temperature, abnormal pressure, and excessive film thickness, the system will immediately issue an alarm signal and automatically take corresponding protective measures, such as stopping equipment operation, cutting off power, etc., to avoid equipment damage and product quality problems. At the same time, the system also has fault diagnosis function, which can help maintenance personnel quickly locate the cause of the fault and improve the maintenance efficiency of the equipment.

The working principle of the three-layer co extrusion blown film machine is based on co extrusion technology, which involves melting three different plastic materials through three independent extruders, and then extruding them simultaneously through a co extrusion die to form a three-layer composite film. The three materials enter their respective extruders, and through heating and the rotation of the screw, the solid plastic is melted into a viscous flow state.

In the context of increasingly strict environmental requirements, three-layer co extrusion blown film machines will pay more attention to the application of energy-saving and environmental protection technologies. For example, adopting efficient heating systems and energy-saving motors to reduce equipment energy consumption; Optimize cooling system design, improve cooling efficiency, and reduce water resource consumption; At the same time, develop co extrusion technology for biodegradable plastic raw materials to meet the demand for environmentally friendly packaging.