How to optimize the parameters of a three-layer co extrusion blown film machine?

The three-layer co extrusion blown film machine is an efficient equipment widely used in plastic film production, and its debugging process directly affects the quality and production efficiency of the film. In order to obtain better production parameters, debugging work needs to start from multiple aspects such as equipment inspection, process parameter setting, material selection, and operational skills.

1、 Equipment inspection and preparation

Equipment cleaning

Before debugging, ensure that all components of the three-layer co extrusion blown film machine are clean and free of contamination, especially key parts such as the mold head, screw, and filter screen. Residual impurities or old materials can affect the uniformity and surface quality of the film.

Check the heating system

Ensure that the heating system of each layer extruder is working properly and the temperature control is accurate. Use a thermometer or infrared thermometer to check whether the actual temperature is consistent with the set temperature, in order to avoid material plasticization or overheating decomposition caused by temperature deviation.

Check the cooling system

The cooling system is the key to film forming, ensuring smooth flow of cooling devices such as air and water rings, flexible adjustment of air and water volume, to ensure the cooling effect and thickness uniformity of the film.

Check the transmission system

Check the smooth operation of transmission components such as traction rollers and winding rollers to ensure no slipping or jamming, and to avoid uneven stretching or wrinkling of the film.

2、 Material selection and proportioning

Material selection

Select appropriate raw materials based on the application of the film, such as polyethylene (PE), polypropylene (PP), ethylene vinyl acetate copolymer (EVA), etc. The selection of materials for each layer should consider their complementary properties, for example, the outer layer material should have good wear resistance and printability, the middle layer material should have good barrier properties, and the inner layer material should have good heat sealing properties.

Material ratio

The material ratio of each layer of the three-layer co extrusion blown film machine needs to be optimized according to the performance requirements of the film. For example, if high-strength thin films are required, the proportion of intermediate layer materials can be appropriately increased; If good heat sealing performance is required, the proportion of inner layer material can be increased. During debugging, it is necessary to gradually adjust the ratio and observe the performance changes of the film.

3、 Process parameter setting

extrusion temperature

The temperature setting of each layer extruder needs to be adjusted according to the melting characteristics of the material. Generally speaking, the temperature of the outer layer material is slightly higher than that of the middle and inner layers to ensure that the material is fully plasticized and has good fluidity. During debugging, it is necessary to gradually adjust the temperature and observe the surface quality and thickness uniformity of the film.

screw speed

The screw speed directly affects the extrusion amount and plasticizing effect of the material. During debugging, it is necessary to adjust the screw speed of each layer extruder according to the thickness and production speed of the film, to ensure that the extrusion amount of each layer of material matches, and to avoid film layering or uneven thickness caused by uneven extrusion amount.

Gap between mold heads

The die gap is a key parameter that affects the uniformity of film thickness. During debugging, it is necessary to adjust the gap between the mold heads according to the thickness requirements of the film to ensure uniform distribution of materials in each layer. If the gap is too small, it may cause the film to be too thin or crack; If the gap is too large, it may cause the film to become too thick or bubbles to appear.

blow up ratio

The inflation ratio is the ratio of the film diameter to the die diameter, which directly affects the tensile strength and thickness uniformity of the film. During debugging, the inflation ratio should be adjusted according to the purpose of the film, generally between 2:1 and 4:1. If the inflation ratio is too high, it may cause the film to be too thin or unevenly stretched; If the inflation ratio is too small, it may lead to excessive thickness or insufficient strength of the film.

Traction speed

The traction speed directly affects the thickness and production efficiency of the film. During debugging, the traction speed should be adjusted according to the thickness requirements and production speed of the film to ensure uniform stretching of the film and avoid thinning or wrinkling due to excessive traction speed.

4、 Operation skills and precautions

Gradually debug

During debugging, it is necessary to gradually adjust each parameter to avoid making significant adjustments at once that may cause the film quality to lose control. After each adjustment, it is necessary to observe the surface quality, thickness uniformity, and physical properties of the film, and record better parameter combinations.

Observe the quality of the film

During the debugging process, it is necessary to closely observe the surface quality of the film, such as whether there are defects such as bubbles, fish eyes, wrinkles, and delamination. If any problems are found, relevant parameters such as extrusion temperature, screw speed, die gap, etc. should be adjusted in a timely manner.

Recording and optimization

During the debugging process, it is necessary to record in detail the set values of each parameter and the quality performance of the film, in order to facilitate subsequent optimization and adjustment. Through multiple debugging and optimization, gradually find a better combination of production parameters.

5、 Common problems and solutions

Uneven film thickness

Possible reasons: uneven die gap, mismatched extrusion volume, and unstable traction speed.

Solution: Adjust the die gap, optimize the screw speed of each layer extruder, and check the stability of the traction system operation.

There are bubbles on the surface of the film

Possible reasons: high moisture content of the material, high extrusion temperature, and small die gap.

Solution: Dry the material, lower the extrusion temperature, and adjust the die gap.

Thin film layering

Possible reasons: poor compatibility of materials in each layer, mismatched extrusion volume, and uneven die temperature.

Solution: Optimize the material ratio, adjust the screw speed of each layer extruder, and check the temperature distribution of the die head.

The debugging of a three-layer co extrusion blown film machine is a complex and meticulous process that requires comprehensive consideration of equipment status, material properties, process parameters, and operating skills. By gradually debugging and optimizing, a better combination of production parameters can be found to ensure the quality and production efficiency of the film. During the debugging process, it is necessary to closely observe the quality performance of the film, adjust relevant parameters in a timely manner, and record debugging data in detail to provide reference for subsequent production.