During the process of plastic bag blown film molding, there are some key points to pay attention to in order to ensure the production of high-quality films and optimize production efficiency. The following are several aspects that need to be paid attention to during the blown film molding process:
1. Raw material selection
Material type: Select appropriate raw materials according to the purpose of the product, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), etc.
Material quality: The use of high-quality raw materials can ensure the strength, transparency and toughness of the blown film, and avoid impurities affecting the quality of the film.
2. Extruder operation
Temperature control: The temperature of each zone of the extruder should be strictly controlled to avoid material degradation or poor plasticization due to improper temperature. Usually, the temperature of the barrel, screw and die head needs to be adjusted according to the material used.
Screw speed: Adjust the screw speed to control the melt flow rate, ensure uniform extrusion of the material, and avoid uneven film thickness due to too fast or too slow speed.
3. Blowing ratio and stretch ratio
Blowing ratio (BUR): refers to the ratio of the diameter of the blown bubble to the diameter of the die. The appropriate blow-up ratio can ensure the strength and transparency of the film. Generally speaking, a larger blow-up ratio can improve the transverse strength and transparency of the film, but too large a blow-up ratio will cause uneven film thickness.
Stretch ratio (DR): refers to the longitudinal stretching degree of the film. An appropriate stretch ratio can improve the longitudinal strength and toughness of the film, but too high a stretch ratio can cause the film to break or deteriorate in quality.
4. Cooling system
Cooling speed: The cooling speed of the film is controlled by adjusting the temperature and wind speed of the cooling air. Too fast cooling speed will increase the brittleness of the film, and too slow cooling speed will cause the transparency of the film to decrease.
Air ring design: Good air ring design and air flow control can help evenly cool the bubbles, prevent bubble instability and uneven film thickness.
5. Die and bubble stability
Die cleaning: Clean the die regularly to prevent melt residue and impurity accumulation, ensuring a smooth and defect-free film surface.
Bubble stability: Maintain the stability of the bubble by adjusting the traction speed, blowing volume and wind ring wind speed to prevent bubble deviation and uneven film.
6. Thickness control
Thickness gauge: Use an online thickness gauge to monitor the film thickness and adjust production parameters in time to ensure that the film thickness is uniform and meets the specifications.
Film uniformity: Control the uniformity of the film by adjusting the extrusion speed, die gap and traction speed.
7. Environmental conditions
Temperature and humidity: The ambient temperature and humidity of the workshop will also affect the quality of the blown film. Keep the workshop temperature stable to avoid excessively high or low temperatures that affect material properties and blown film quality.
Cleanliness: The cleanliness of the production environment is also very important to avoid dust and impurities from mixing into the film and affecting product quality.
8. Operator experience and skills
Training: Operators should receive professional training and be familiar with the operating procedures of the blown film equipment and the adjustment methods of various parameters.
Monitoring and adjustment: Operators need to monitor various parameters in the production process in real time and make timely adjustments based on product quality.
By paying attention to these key points, the quality and efficiency of plastic bag blown film molding can be effectively improved, the defective rate in production can be reduced, and the overall production effect can be improved.
