CNC machining technology has been widely favored by manufacturers due to its high efficiency, good quality and strong stability. In recent years, with the rapid development of CNC process equipment and CNC technology at home and abroad, CNC machining technology has been widely used. Especially plays a decisive role in the manufacture of aircraft body parts. The project of China's large-scale aircraft project is a rare historical opportunity for aircraft manufacturers and equipment manufacturers. It is also a historical challenge for the dream of the People's Congress of the People's Republic of China. This paper makes a preliminary study on the application of CNC machining technology in the development of large aircraft. Explore.
I. Technical requirements for CNC machining of large aircraft
1. CNC machining technology for typical parts
The large aircraft parts have the characteristics of large outer dimensions, complicated structure and light weight, and there are multi-faceted joint parts with high precision requirements at multiple docking parts or movable surfaces. At the same time, with the continuous development of new material technology and the continuous improvement of the overall strength and weight ratio of the aircraft, the amount of composite materials used in large aircraft is also increasing. These characteristics of large aircraft parts put forward a series of new requirements for CNC machining technology.
Typical integral parts include wing skin panels, fuselage skin panels, wing girders, ribs, etc. These parts are generally selected from 2000 series or 7000 series aluminum alloy pre-stretched sheets, and some rib parts are made of aluminum. The alloy profile raw materials, in addition to the large size of the parts, also exhibit structural features such as multi-cavity, single-sided or double-sided theoretical shape. The siding parts generally have a theoretical shape and a one-sided structure of a single-sided aircraft, and need to be shot blasted or rolled during the processing. Parts such as girders and ribs are generally double-sided theoretical shape, single-sided or double-sided structure, and the part structure is directly completed by numerical control machining. Except for the ribs of some double-sided structures, the parts are all single-sided structures. During the processing, the materials are basically removed on one side, and the material removal rate is large. Therefore, the numerical control machining of large-scale integral parts must consider the comprehensive application of five-axis machining technology, high-speed and high-efficiency machining technology and numerical control machining deformation control technology of complex structure.
Typical joint parts include main landing gear support joints, spoiler hinge joints, and wing and fuselage butt joints. These parts are generally 7000 series die forged or free forged aluminum alloy materials. The depth of the cavity and the accuracy and position of the space hole are required to be high. The processing difficulty of such parts mainly lies in the processing of deformation control, deep groove cavity surface quality control and digital precision hole processing, and for free forging parts, the material removal rate is also a factor to be considered. Therefore, complex joint parts need to develop a reasonable process flow, while paying attention to the comprehensive application of corner insertion milling technology, CNC boring and milling composite machining technology.
The industrial application of composite technology such as carbon fiber has brought a new world to the design and manufacture of large aircraft. Composite materials have been widely used in the structure of large aircraft due to their high corrosion resistance and fatigue resistance, such as B787. The composite material of the aircraft accounts for 50% of the weight of the overall structure and has been completely changed from auxiliary materials to dominant materials. Processing of composite materials In addition to the laying technology and winding technology, CNC trimming and CNC drilling are also indispensable, especially for CNC machining of large-scale composite composite components. The difficulty lies in the low thermal conductivity of the material itself. The speciality of positioning and clamping, therefore, the numerical control machining of composite materials is mainly reflected in the design and manufacturing technology of CNC cutting tools and their application technology and tooling.
2. High speed machining technology
The realization of large-scale NC machining technology must rely on advanced CNC equipment and high-quality CNC tools that meet the requirements of use. In other words, CNC equipment must have large stroke, high speed, high feed, high precision and five-axis linkage. Features; CNC tools must meet the technical requirements of high dynamic balance grade, high rigidity, good wear resistance and red hardness. Tool interface technology must also meet the technical requirements for high-speed use.
The successful application of high-speed machining technology is a revolution in the development of CNC machining technology. When the cutting speed exceeds a certain critical speed, the cutting force decreases with the increase of speed, and more than 95% of the cutting heat is high speed. The flying chips are taken away, so high-speed machining has unparalleled advantages in improving cutting efficiency, suppressing machining distortion and improving surface finish quality. At the same time, due to its beneficial effect on the processing deformation control, the process flow is greatly simplified, and the processing cycle of the parts is further reduced. The technical requirements for large-scale, integral aircraft structural parts for CNC machining are mainly reflected in the small machining deformation and surface quality in accordance with the design requirements, and at the same time, a higher material removal rate must be required from the viewpoint of reducing the processing cost. Therefore, high-speed machining technology is an effective way to break through the bottleneck of the development of key parts of large aircraft, and it is of great significance to reduce the manufacturing cost of large parts.
3. Integrated application technology of CNC machining
Economicality is one of the important indicators of large aircraft. Due to the high cost of numerical control equipment, the assembly of large aircraft components must realize the integrated application of numerical control machining, so that the advantages of numerical control equipment and numerical control technology can be fully utilized to reduce manufacturing costs. The application of modern advanced manufacturing systems and technologies such as CAD/CAPP/CAM integrated systems, MES systems, ERP systems, and DNC technologies in large aircraft manufacturing processes will greatly reduce the cost of manufacturing the aircraft and will be critical to the economic indicators of the aircraft. Important role.
