Although the skin is thin, it is important for safety
Don't let the skin become a "source of hidden dangers"
In 2002, China Airlines Flight 611 disintegrated and crashed over the Taiwan Strait on its way to Hong Kong International Airport. Subsequent investigation results revealed that the tail skin (the outermost riveted metal shell) of the aircraft was damaged as early as 22 years ago due to a heavy landing accident. However, China Airlines did not replace the entire skin in accordance with the maintenance guidelines formulated by Boeing, but simply covered it with an aluminum plate. This treatment method caused metal fatigue to accumulate in the area, and eventually cracked, causing the aircraft to lose pressure and disintegrate in the air.
In the field of aerospace, the surface precision machining accuracy of aircraft skin, engine blades, landing gear and various precision parts is a key factor in ensuring the performance, safety and service life of aircraft. Even extremely subtle flaws may be magnified in extreme operating environments, leading to serious consequences.
The exquisite "skin care" of aircraft
Surface precision machining technology reveals
As the appearance part of the aircraft, the aircraft skin is like a solid "skin" that isolates the complex internal systems of the aircraft from the external environment. It is tightly attached to the aircraft's skeleton structure through adhesives or rivets to form the aerodynamic shape required by the aircraft, accounting for about 80% of the fuselage area and 21% of the weight. Usually, it is made of aluminum alloy, titanium alloy and composite materials.
Given its large area, complex structure and low rigidity, in order to ensure that the skin has good surface smoothness and excellent corrosion resistance to ensure long-term stable operation, it must rely on the support of a variety of surface precision processing technologies.
It should be noted that the dimensional accuracy and shape accuracy of the skin are crucial to the overall assembly quality of the aircraft. During the manufacturing process, deburring, grinding and polishing processes can accurately control the thickness and shape of the skin to ensure that it meets the design tolerance requirements. This is crucial to achieve precise docking between the skin and other key components, such as the wing skeleton and fuselage frame, and helps to enhance the overall structural strength and stability of the aircraft.
For example, during the installation of the wing skin, if there are large burrs on the surface or it is not precisely ground or polished, it may cause gaps or poor fit between the skin and the skeleton, thereby affecting the aerodynamic performance of the wing and its structural integrity.
Next, let's discuss in detail the importance of deburring, grinding and polishing technologies for aircraft skins.
Mechanical deburring, chemical deburring and other technologies for skins
During the manufacturing process of aircraft skins, whether it is mechanical processing or other forming methods, its surface will inevitably produce tiny burrs. In order to achieve a smoother surface effect and lay a good foundation for subsequent grinding and polishing processes, it is usually necessary to use a variety of deburring technologies including mechanical, chemical, electrolytic and ultrasonic.
Mechanical deburring uses professional equipment, such as vibrating deburring machines and magnetic deburring machines, to impact and rub the skin surface with high-speed rotating or vibrating abrasives, thereby effectively removing burrs. This method is efficient and suitable for processing large areas and regular shapes, and can provide a relatively uniform and consistent deburring effect.
Chemical deburring is to treat the skin surface with specific chemical reagents to dissolve or soften the burrs, and then remove these burr residues by means of flushing. This method is suitable for those situations where high surface accuracy is required and the burrs are relatively small. However, when chemical deburring is performed, chemical agents must be carefully selected and used to avoid corrosion or other forms of damage to the skin material.
Skin rough grinding, fine grinding and other technologies
The grinding and polishing process can further eliminate the microscopic unevenness and fine defects on the surface of the aircraft skin, ensuring that the surface roughness reaches extremely high precision standards, which is crucial to reducing air resistance during flight.
In addition, when the aircraft is flying at high altitudes, it will encounter various complex meteorological conditions and environmental factors including low temperature, high humidity and ultraviolet radiation, which may cause corrosion to the skin. Through meticulous grinding and polishing, not only can the skin surface be smoother, but also a uniform and dense oxide film or other protective layer can be formed, which significantly improves its corrosion resistance. It helps to maintain the structural integrity and appearance of the aircraft, extend its service life, and enhance safety and economy.
The rough grinding process uses coarse-grained sandpaper or a grinder to quickly remove burrs, weld scars and other protrusions on the surface of the aircraft skin, so that the surface is roughly flat. When performing rough grinding, special attention should be paid to controlling the strength and speed of grinding to avoid material damage due to excessive grinding.
Fine grinding is carried out on the basis of rough grinding. By using fine-grained sandpaper or grinding head to perform more delicate treatment on the skin surface, the surface is further smoothed and its quality is improved.
Compared with rough grinding, fine grinding requires higher precision and patience to ensure that the final surface is free of scratches and unevenness. This process is crucial to achieving high standards of surface finish. It can provide an ideal preparation surface for subsequent mechanical, chemical, electrochemical and other polishing processes. It can not only give the surface of parts a mirror-like gloss, but also enhance its wear resistance and fatigue strength. It is also directly related to the aerodynamic performance and appearance quality of the aircraft.
Skin chemical polishing, electrochemical polishing and other technologies
Chemical polishing is to treat the skin surface with chemical reagents to achieve the polishing effect by inducing chemical reactions on the surface of the material. This method can effectively remove the oxide layer and dirt on the surface, while improving the corrosion resistance and glossiness of the surface. This process is easy to operate and is suitable for complex shapes and hard-to-reach surfaces, ensuring the consistency and reliability of the overall quality of the skin.
Electrochemical polishing is a method of treating the skin surface based on the principle of electrolysis. By precisely adjusting the electrolysis parameters and the composition of the polishing liquid, the polishing effect is strictly controlled to obtain a high-quality smooth surface. This method can evenly polish surfaces with complex shapes and fine structures, ensuring that even hard-to-reach areas can be effectively treated, and is suitable for polishing skins made of various metal materials.
Precision parts
Overall solution for surface precision machining technology
There are many types of deburring, grinding, and polishing technologies for aircraft skins, and each technology has unique advantages and scope of application. In the actual manufacturing and maintenance process, it is necessary to comprehensively consider factors such as the material, shape, surface quality, and production requirements of the skin to select the most suitable technical solution. And with the advancement of technology and the emergence of new processes, the surface precision machining technology of aircraft skins is also continuing to develop and improve.
And with the growth of automation demand in the manufacturing industry, robot deburring, grinding, and polishing technologies will be more widely used, automatically and precisely process skins, reduce labor costs and operating errors, and strongly support the development of the aviation industry. Of course, in addition to skin deburring, grinding and polishing technologies, other surface precision processing technologies are also crucial. For example, the aircraft skin is in direct contact with the outside world and is susceptible to corrosion in a complex environment, so the outer side needs to be coated and treated.(文章来源：国际金属加工网,如有侵权,请联系删除)
