Why is the film thickness of the film blown by the film blowing machine uneven?

The influence of film blowing machine components or settings on film thickness uniformity

Extrusion system
The extrusion system of the film blowing machine is considered to be one of the core elements that determine the consistency of film thickness. Through the analysis of the extrusion mechanism of the PLA PBAT Biodegradable Film Blowing Machine, a method of using a variable frequency motor to control the screw rotation speed to adjust the extrusion port material amount to improve the film quality is proposed. The structure and rotation speed of the screw will directly determine the degree of extrusion and the distribution of pressure of the melt, which will further affect the thickness of the film. Due to the complexity of the screw structure and working conditions, there are a lot of nonlinear factors in the extruder. The size of the screw, such as diameter, aspect ratio and thread shape, all affect the plasticity and extrusion process of the melt. Therefore, these factors must be considered during design and manufacturing to ensure that the film thickness meets the design requirements. In addition, the shape and size of the die head play a key role in the uniformity of the film thickness. This paper studies the relationship between screw parameters and melt flow patterns at different pitches. The flow channel design of the die head, the size and shape of the outlet will affect the flow condition and distribution of the melt, and then determine the uniform thickness of the film.
Cooling system
The cooling system plays a vital role in ensuring the uniform thickness of the film produced by the PLA PBAT Biodegradable Film Blowing Machine. The cooling air ring type film blowing machine is a new type of film cooling device. It uses a fan to send cold air into the film roll, take away the heat from the outer surface of the film roll and discharge it through the air duct. By adjusting the cooling air ring, we can manage the air volume and wind direction of the cooling air, thereby affecting the cooling rate and temperature distribution of the film. Therefore, by changing the hole structure of the cooling air ring, the purpose of improving the cooling effect of the film layer can be achieved. If unevenness occurs during the cooling process, this will cause the film to shrink and deform during the cooling stage, which will have an adverse effect on the thickness uniformity of the film. The cooling air flow rate is adjusted by changing the cooling water flow rate to achieve the purpose of improving the thickness uniformity of the film and improving product performance. In addition, the speed of cooling will also affect the crystallinity and mechanical properties of the film, thereby affecting the thickness uniformity of the film.
 Traction and winding system
The thickness uniformity of the film is largely affected by the traction and winding system. In order to obtain higher tensile strength and good surface flatness, the traction system needs to be precisely controlled. The degree of stretching and stress distribution of the film are directly affected by the pulling speed and tension control, which further affects the thickness of the film. Therefore, it is crucial to effectively control the pulling force and tension. When the pulling speed is inconsistent or the tension is too high, the film may become thinner or thicker in part during the stretching process. Choosing a suitable winding method will also affect the winding effect and thickness consistency of the film.
The influence of raw material properties and formulation on the uniformity of film thickness
Raw material properties
The physical properties of plastic particles, such as melt index and density, directly determine the flow characteristics and extrusion process of the melt, thereby affecting the thickness uniformity of the film. Different materials have their own characteristics and requirements. Raw materials with high melt index have good fluidity, which makes them easier to extrude and form, but this may also cause inconsistent film thickness. Therefore, increasing the melting point of plastic particles is one of the keys to obtaining thinner films. During the extrusion process, high-density raw materials are more difficult to maintain their flow conditions, which may also affect the thickness uniformity of the film. In addition, due to the large number of defects or additives in the raw materials themselves, the film is prone to cracks, wrinkles, delamination, warping and even rupture. In addition, factors such as impurities and moisture in the raw materials may also have a certain impact on the thickness uniformity of the film.
Formula adjustment
The thickness uniformity of the film is largely affected by the type and amount of additives. The use of different types of additives in the film production process will have a great impact on the thickness uniformity of the film. Plasticizers help to improve the fluidity and toughness of plastics, thereby optimizing the processing properties of the film, but excessive plasticizers may also cause uneven film thickness. Stabilizers help maintain the stability of plastics and prevent them from decomposing or changing color during the manufacturing process, but they may also have an adverse effect on the thickness uniformity of the film. In addition, additives can also reduce the roughness of the film surface, improve anti-pollution ability, and improve the mechanical properties of the film. Therefore, by properly adjusting the type and amount of additives in the formula, it is helpful to improve the thickness consistency of the film.

Uneven film thickness caused by human factors
Operating skills
The operator has a deep understanding and adjustment skills for the parameters of the film blowing machine, which directly determines whether the thickness of the film is uniform. The data obtained after the film was tensile tested at different temperatures were analyzed to analyze the operator's control of film quality and film thickness. If the operator is not familiar with the working parameters of the film blowing machine or makes inappropriate adjustments, it may cause uneven film thickness. In addition, incorrect operations during operation may also cause inconsistent film thickness, such as excessive screw speed adjustment or inappropriate adjustment of the cooling air ring.
 Monitoring and maintenance
Regular inspection and maintenance of the film blowing machine is a key step to ensure uniform film thickness. The film blowing machine is mainly composed of a drive mechanism, a film conveying device and a control system. If the PLA PBAT Biodegradable Film Blowing Machine is not properly maintained or serviced for a long time, it may cause problems such as reduced equipment performance and component wear, thereby affecting the uniformity of film thickness. In daily production, the accuracy of film thickness can be ensured by regular inspection and timely adjustment of parameters. In addition, by using a monitoring system, we can quickly identify and deal with problems encountered in production to ensure that the thickness of the film remains consistent.
The impact of the production environment on the uniformity of film thickness
Temperature changes
The film blowing process is directly affected by fluctuations in workshop temperature. When the ambient temperature exceeds a certain value, the film blowing machine will not work properly. Whether the temperature is too high or too low, it may change the flow characteristics of the melt and the extrusion process, thus adversely affecting the thickness uniformity of the film. To achieve this goal, reasonable and effective means must be used to control the temperature distribution of the workshop. Therefore, throughout the production process, we must strictly manage the temperature of the workshop to ensure that it is always in a stable range. Through experiments, the quality characteristics of the film under different process conditions and the impact on product performance were analyzed, and the temperature distribution law of raw materials and molds and their mutual influence were studied. Similarly, the temperature management of raw materials and molds is also very critical. Whether the temperature of the raw material is too high or too low, it will affect its melting condition and extrusion process; the uneven temperature of the mold may cause the film to shrink and deform during cooling, which will have an adverse effect on the thickness uniformity of the film.
Humidity changes
Humidity plays a key role in the melting and cooling of raw materials. After drying, the raw materials are prone to agglomeration, causing agglomeration, lumps and even adhesion between materials, thereby reducing product performance. If the humidity is too high, the raw material may absorb too much water, which will have an adverse effect on its melting state and extrusion process; if the relative humidity is too low, the surface of the raw material will dry, thereby reducing the surface quality of the product and being unfavorable for processing and molding. If the humidity is too low, it may cause undesirable phenomena such as static electricity or adhesion during the extrusion of the raw material. In addition, humidity changes can also cause wrinkles and breaks on the surface of the film, which can seriously cause product quality to deteriorate. Therefore, throughout the production process, we must strictly manage the humidity of the workshop to ensure that it is maintained at an appropriate level. The use of spray cooling technology can well control the temperature distribution and relative humidity changes, thereby improving the quality of the finished product and reducing production costs. In addition, proper drying of the raw materials can significantly reduce the adverse effects of humidity on the uniformity of film thickness.
Detection and adjustment of the film blowing machine to ensure uniform film thickness
Detection method
In order to ensure that the film generated by the PLA PBAT Biodegradable Film Blowing Machine has a uniform thickness, it is necessary to use efficient detection methods. Among the film thickness measurement methods, the most common and widely used is the optical method. Film thickness measurement equipment is one of many detection tools that can accurately measure the thickness of the film and evaluate its uniformity. In the actual production process, the film thickness measuring instrument can accurately control the product according to user requirements. In addition, the online monitoring system can track the changes in film thickness during the production process in real time, so as to identify and deal with related problems in time. By analyzing the principles, characteristics and applicable scope of various detection methods, an online detection scheme based on laser interference technology and photoelectric conversion technology is proposed. The application of these detection technologies can significantly improve production efficiency and product quality.
Adjustment strategy
Based on the detection data, we can make appropriate adjustments to the film blowing machine to ensure that the film thickness is more uniform. This paper introduces a method to improve the thickness uniformity of the film by adjusting the process conditions. First, we can adjust the key parameters such as the screw speed and the cooling air ring according to the measurement data of the film thickness measuring equipment to achieve a more uniform distribution of the film thickness. At the same time, the heating power can be increased or the temperature can be reduced to improve the thickness uniformity of the film, thereby obtaining a higher yield. Next, we can thoroughly clean and replace the mold, which can reduce the adverse effects of mold wear or blockage on the thickness uniformity of the film. Thirdly, different heating methods can be used to increase the temperature of the film during blowing, so that it can better adapt to the blowing process conditions. In addition, we can also enhance the screening and drying process of raw materials to reduce the adverse effects of impurities and moisture in the raw materials on the thickness uniformity of the film. At the same time, building a comprehensive preventive maintenance and fault diagnosis process is also a key means to ensure the consistency of film thickness.

Taking into account, there are many factors that lead to inconsistent film thickness produced by film blowing machines, including the components or configuration of film blowing machines, the properties and formulation of raw materials, human intervention, and production environment. Among them, the composition and ratio of raw materials affect the thickness uniformity of the film, and the production process conditions play an important role in the thickness uniformity of the film after film blowing. In order to ensure the uniform thickness of the film, we must adopt efficient detection methods and adjustment strategies. Among them, reasonable design and selection of film blowing machines, selection of suitable raw materials, improvement of process operation methods, and control of temperature in the production process are all very important links. By continuously improving the parameters and configuration of film blowing machines, strengthening the screening and drying of raw materials, improving the professional skills and monitoring level of operators, and strictly controlling the production environment, we can effectively improve the thickness uniformity of the film produced by film blowing machines, thereby improving product quality and production efficiency.