How to choose a three-layer co extrusion blown film machine? What are the key core configurations to consider

The three-layer co extrusion blown film machine, with its advantage of being able to composite different materials (such as PE, PA, EVOH, etc.), can produce high-performance films with barrier properties, strength, and transparency, which are widely used in food packaging, pharmaceutical packaging, industrial protection, and other fields. When making a purchase, it is necessary to focus on the five core configurations of extrusion system, die head, cooling system, traction winding, and control system, and make a comprehensive judgment based on one's own production needs (product type, output, quality requirements). The following is a deep analysis of key configurations:

1、 Extrusion system: the "source guarantee" of film quality

Three independent extruders are required for three-layer co extrusion, each responsible for the melting and conveying of different layers of raw materials. Their performance directly determines the uniformity and physical properties of the film.

Screw and barrel

Screw type: Select the appropriate screw according to the raw material - such as barrier type screw for processing PE (enhancing melt mixing and reducing crystal points); Separate screws are used for processing PA/EVOH and other barrier materials to avoid material degradation; The length to diameter ratio (L/D) is recommended to be 1:281:33 (taking into account both melting efficiency and mixing uniformity), and the compression ratio needs to be matched with the raw materials (PE 3:14:1, PA 2.5:1~3:1).

Material of material barrel: Double metal material barrel (coated with tungsten carbide alloy) is preferred, with wear resistance 3-5 times that of ordinary nitride steel, suitable for processing materials containing fillers (such as calcium carbonate) or corrosive materials; The surface of the screw needs to be treated with nitriding or sprayed with hard alloy to reduce sticking and wear.

drive system

Recommended servo motor drive (replacing traditional asynchronous motors): The speed control accuracy reaches ± 0.1rpm, saving more than 20% energy, and can achieve synchronous linkage between screw speed and traction speed, avoiding film stretching deformation.

2、 Die head system: the "key center" of film thickness uniformity

The die head is the core component for converting raw materials into thin films, and its flow channel design and adjustment capability directly affect the thickness tolerance of the thin film.

Die type

Spiral die head: The flow channel is distributed in a spiral shape, resulting in more uniform mixing of molten materials. The thickness tolerance of the film can be controlled within ± 2%, making it suitable for high-quality packaging (such as food vacuum bags); But the cost is relatively high.

Branch tube mold head: The flow channel is a branch tube+distribution chamber structure, which has low cost but poor uniformity (tolerance ± 5%), and is only suitable for low demand industrial packaging.

It is recommended to prioritize the use of spiral die heads (especially those with high uniformity requirements for the barrier layer in three-layer co extrusion).

adjustment device

Automatic thickness adjustment: such as thermal expansion bolt adjustment (changing the lip gap by heating the bolt expansion) or piezoelectric ceramic adjustment, it can correct the thickness deviation of the film in real time (with an accuracy of 0.01mm); Manual adjustment (such as mechanical bolts) has low accuracy and is only suitable for small-scale production.

Material: The inner surface of the mold head needs to be polished (roughness Ra ≤ 0.2 μ m), and the material should be hard alloy or chrome plated stainless steel to prevent the molten material from sticking to the wall and degrading.

3、 Cooling System: Accelerator for Film Appearance and Efficiency

The cooling effect determines the transparency, flatness, and production speed of the film, while balancing uniformity and stability.

Wind ring structure

Recommended double-layer air ring or circular air knife: The upper and lower air nozzles of the double-layer air ring can independently adjust the air volume, resulting in more uniform cooling; The wind speed of the circular air knife is higher (up to 30m/s), and the cooling efficiency is increased by 20%, making it suitable for high-speed production (≥ 150m/min).

Some high-end models are equipped with zone adjustable air rings (such as 8-12 zones), which can adjust the air volume according to different positions of the film circumference, reducing thickness deviation.

Cooling control

Constant temperature cooling system: Real time monitoring of cooling air temperature (± 1 ℃) through temperature sensors to avoid uneven film shrinkage caused by environmental temperature fluctuations; Some models are equipped with water-cooled air rings to further improve cooling efficiency.

4、 Traction winding system: the "stable backing" for film forming

The stability of traction winding directly affects the flatness and winding quality of the film, and it is necessary to avoid slipping, wrinkling, and loosening.

Traction device

Traction roller: Choose silicone coated roller (hardness 70-80 Shore A), with good elasticity and wear resistance, which can tightly adhere to the film and prevent slipping; The roller surface needs to undergo dynamic balancing treatment (≤ 0.05g · cm) to avoid wrinkling of the film caused by vibration.

Drive: Driven by a servo motor, the traction speed is synchronized with the extrusion speed with an accuracy of ± 0.5%, ensuring stable film stretching ratio.

Winding device

Roll up method: center roll up (suitable for large roll diameters, such as 1.5m or more) or surface roll up (suitable for thin films); Prioritize automatic tension control winding (real-time adjustment of winding torque through tension sensors) to avoid film stretching deformation or loosening.

Roll up neatness: Equipped with an automatic correction system (such as photoelectric sensors+servo correction rollers) to ensure that the edge alignment deviation of the film is ≤ 1mm.

5、 Control system: the 'brain' of production accuracy

The control system needs to achieve multi parameter linkage and precise regulation to reduce manual intervention errors.

Core configuration: PLC control system+touch screen operation, supporting parameter storage (such as 100 sets of formulas), real-time data monitoring (extrusion temperature, screw speed, traction speed, etc.), and fault alarm (such as temperature abnormality, film breakage).

High end features:

Online thickness measurement system (such as beta ray thickness gauge): Real time monitoring of film thickness, automatic feedback adjustment of die thickness or traction speed, thickness tolerance controlled within ± 1%;

Energy consumption monitoring system: Statistics of energy consumption of various components and optimization of production processes.

6、 Auxiliary configuration and after-sales service

Auxiliary configuration:

Raw material drying system: For moisture absorbing materials such as PA/EVOH, a dehumidification dryer (dew point ≤ -40 ℃) should be equipped to avoid the formation of bubbles in the film;

Automatic feeding system: reduces manual contact, prevents raw material contamination, and improves efficiency.

After sales service: Priority should be given to manufacturers that provide installation and debugging, technical training, and spare parts supply (such as screws and mold vulnerable parts) to ensure long-term stable operation of the equipment.

summary

When selecting a three-layer co extrusion blown film machine, it is necessary to make a comprehensive judgment based on the product positioning (high-end/mid low end), raw material type (PE/PA/EVOH), and production scale:

High quality requirements (such as food packaging): choose spiral die head+servo drive+automatic thickness adjustment+online thickness measurement;

Mid to low end demand (such as industrial packaging): optional branch pipe die head+asynchronous motor+manual adjustment;

High speed production: Priority is given to double-layer wind rings and servo traction winding.

The stability, accuracy, and efficiency of the equipment are core indicators, and their performance needs to be verified through on-site inspections of manufacturer cases (such as similar product production lines) to ensure maximum return on investment.