How To Solve The Technical Difficulties in Aluminum Alloy Processing in Aerospace?

1. The main technical challenges faced by aluminum alloy processing in aerospace
(1) Processing deformation problem
Aluminum alloy has relatively low hardness and a high coefficient of thermal expansion, making it prone to deformation in the mechanical processing of thin-walled and thin plate parts. For example, when milling aluminum alloy plates, if a single-sided one-time machining process is used, due to heat concentration, it will result in poor flatness. For parts with cavities, if the method of sequentially processing cavities is used, it will cause uneven stress on the cavity wall and deformation.
(2) Surface quality challenges
Aluminum alloys are prone to surface roughness, scratches, burrs, and other issues during processing, which can affect the appearance quality and performance of the parts. Especially in some aerospace components that require extremely high surface quality, such as engine blades, satellite antenna reflectors, etc., poor surface quality can lead to a decrease in component performance and even affect the normal operation of the entire system.
(3) Low processing efficiency
Due to the processing characteristics of aluminum alloys, such as low cutting force but easy increase in cutting temperature, frequent tool replacement and adjustment of process parameters are required during the processing, thereby reducing processing efficiency. In addition, some complex aerospace component structures, such as parts with multiple cavities and thin-walled structures, are difficult to process and further affect processing efficiency.
(4) Tool wear and fracture
Aluminum alloys are prone to chip deposits during the cutting process, leading to increased tool wear. At the same time, aluminum alloy has good thermal conductivity, and cutting heat is easily conducted to the tool, causing the tool temperature to rise, reducing the hardness and strength of the tool, and easily causing tool fracture. The wear and fracture of cutting tools not only increase processing costs, but also affect processing quality and production efficiency.
2. Strategies for solving the technical difficulties in aluminum alloy processing in aerospace
(1) Optimize processing technology parameters
Selection of cutting parameters: Reasonably choose cutting speed, feed rate, and back cutting amount. Excessive cutting parameters can lead to excessive cutting force, causing part deformation, and affecting the rigidity of the machine tool spindle and tool durability. While reducing the amount of back cutting, increasing the feed rate appropriately and increasing the machine speed can ensure machining efficiency while reducing cutting force. For example, in high-speed milling of CNC machining, optimizing cutting parameters can effectively reduce machining deformation of parts.
Planning of cutting sequence: Different cutting sequences should be used for rough machining and precision machining. Rough machining emphasizes processing efficiency and pursues material cutting rate per unit time, and it is advisable to use reverse milling; Precision machining has higher requirements for machining accuracy and surface quality, emphasizing machining quality and using sequential milling. During sequential milling, the cutting thickness of the teeth gradually decreases from the maximum to zero, which can greatly reduce work hardening and suppress part deformation.
(2) Adopting advanced processing technology
Symmetrical machining method: For aluminum alloy parts with large machining allowance, in order to create better heat dissipation conditions and reduce thermal deformation, it is necessary to avoid excessive heat concentration as much as possible and adopt symmetrical machining method. For example, when milling aluminum alloy plates, a symmetrical machining method with repeated cutting on both sides is used, so that each side is machined at least twice until the final size is reached, and the flatness can be effectively controlled.
Layered multiple processing method: When there are multiple cavities that need to be processed on aluminum alloy sheet parts, the layered multiple processing method is used, which means that all cavities are processed simultaneously, but not in one processing, but in several layers and processed layer by layer to the required size. This way, the force on the parts will be more uniform and the probability of deformation will be smaller.
Additive Manufacturing Technology: Aluminum alloy arc additive manufacturing technology has been widely used in the aerospace industry, and can be used to manufacture lightweight components such as aircraft structural components and wings. By optimizing additive manufacturing process parameters such as laser power, scanning speed, layer thickness, etc., the forming quality and accuracy can be improved, and processing deformation and defects can be reduced.
(3) Strengthen tool management and selection
Tool material selection: Choose the appropriate tool material based on the processing characteristics of aluminum alloy. For example, using hard alloy cutting tools or coated cutting tools can improve the wear resistance and heat resistance of the tools. The coating materials for coated cutting tools can be selected from titanium nitride (TiN), aluminum titanium nitride (TiAlN), etc. These coatings have high hardness, low friction coefficient, and good oxidation resistance, which can effectively reduce tool wear.
Optimization of geometric parameters of cutting tools: Geometric parameters such as rake angle and rake angle of cutting tools have a significant impact on cutting force and cutting heat. Under the condition of maintaining blade strength, increasing the rake angle appropriately can reduce cutting deformation, facilitate chip removal, and thereby reduce cutting force and cutting temperature; The size of the back angle should be selected according to the cutting thickness. During rough milling, the back angle should be smaller, and during fine milling, the back angle should be larger to reduce the friction between the back cutting surface and the machining surface and minimize elastic deformation.
Tool wear monitoring and replacement: Strictly control the wear standards of the tools, and replace them in a timely manner when the tool wear exceeds a certain limit. Adopting advanced tool wear monitoring technologies such as acoustic emission monitoring, laser monitoring, etc., real-time monitoring of tool wear status, early warning of tool failure, and avoiding machining quality problems caused by tool wear.
(4) Strengthen process planning and control
Heat treatment and cold treatment: Artificial aging, recrystallization annealing and other heat treatment methods are used to eliminate processing stress in aluminum alloy materials. For structurally simple parts, the process route generally adopts rough machining, manual aging, and precision machining; For parts with complex structures, the process route generally adopts rough machining, manual aging (heat treatment), semi precision machining, manual aging (heat treatment), and precision machining.
Optimization of clamping method: When processing thin-walled aluminum alloy parts, the clamping force during clamping is an important cause of deformation. In order to reduce the deformation of the workpiece caused by clamping, the clamped part can be loosened before reaching the final size during precision machining, releasing the clamping force to allow the part to freely return to its original state, and then re tightened slightly. The optimal point for secondary compression is on the supporting surface, and the clamping force should be applied in the direction of good rigidity of the workpiece. The magnitude of the clamping force should be based on the ability to clamp the workpiece without loosening.
Innovation in processing technology: Exploring new processing techniques such as laser processing, water jet processing, etc. Laser processing has the advantages of high energy density and non-contact processing, which can achieve high-precision and high-quality processing of aluminum alloys; Water jet machining has the characteristics of no heat affected zone and high machining accuracy, and is suitable for the machining of aerospace components with extremely high surface quality requirements.