Development trend of foreign aircraft advanced manufacturing technology (CNC machining)

Looking at the history of the aircraft manufacturing industry for nearly a hundred years, especially the development history of recent decades, the development of aircraft manufacturing technology is driven by the strong demand for civil transportation and military use, and is driven by the development of the world economy and science and technology, forming a rapid development today. Development and widespread application. 

The arms race in the cold war era has stimulated the development of the military industry, especially the aircraft industry. In order to develop high-performance new fighters, large military transport aircraft, special military aircraft and helicopter gunships, governments and the military have continuously introduced new research plans, invested huge sums of money, developed advanced manufacturing technologies and special equipment, and basically established advanced aircraft manufacturing technologies. The basis of development. 
With the recession of the world economy for a long period of time, the profits of airlines in various countries have fallen sharply, directly affecting aircraft manufacturers. Therefore, in order to survive, reducing the cost of the aircraft's life cycle has become an important indicator for the development of a new generation of civil aircraft and the development direction of advanced manufacturing technology. 

After the end of the Cold War, countries have cut a large amount of defense funds, and the military is unable to withstand the high procurement costs of high-performance weapons and equipment, such as the F-22 fighter jets of $160 million each. Such high procurement costs limit the production of the aircraft, so the US military proposed to develop affordable aircraft - JSF joint attack aircraft (about 300 million each) as a corresponding supplement. The development and production of military aircraft also proposed the dual goals of high performance and low life cycle. 

The continuous development of computer technology, the birth of many new concepts such as lean production, the advanced manufacturing technology of aircraft is constantly changing, the traditional technology is constantly refined, the new materials, new structure processing, forming technology are constantly innovating, the integrated structure and digitalization Manufacturing technology builds the main framework for the advanced manufacturing technology of the new generation of aircraft. In order to further understand this trend of the development of foreign aircraft advanced manufacturing technology, this paper introduces several major manufacturing technologies (the advanced CNC machining technology selected in this station).
The application of numerical control technology to aircraft manufacturing in western industrialized countries began in the 1960s. In the development of numerical control technology in the past 50 years, the development status and application level of numerical control technology in aircraft manufacturing industry in developed countries are mainly reflected in the following aspects: basic realization of machine plus numerical control, extensive use of CAD/CAPP/CAM system and DNC technology, CNC machining has high efficiency, established flexible production lines and developed high-speed machining technology.

1 Basically realized CNC machine tools in developed countries accounted for 30% to 40% of the total number of machine tools, while aviation manufacturing was higher, reaching 50% to 80%. Boeing, McDonnell and other aircraft manufacturing companies are equipped with a large number of different types of advanced numerical control equipment, especially large-scale, multi-coordinate CNC milling and machining centers, and related supporting equipment, high numerical control rate, basic The machine is added to the numerical control. 
Boeing established the aluminum, titanium and steel structural parts machine shop and the wing skin and beam structure machine shop in the Auburn civil aircraft manufacturing division. There are 362 machine equipments and about 180 NC machine tools. Up to 50%. 
In the mid-to-late 1990s, these companies are still further strengthening the technical transformation and updating of machining equipment, especially multi-coordinate high-speed CNC milling machines and machining centers. For example, Boeing's Wichita military manufacturing division is equipped with the French Forest Line 43m×3m×2m overhead 3 gantry 5-coordinate Minumac 30TH CNC milling machine, and the British Airline (BAe) and original Germany for processing the Airbus aircraft structural components. Hamburg DASA and Remele, which is responsible for the manufacture of Bell's helicopter structural parts, are equipped with high-speed 5-axis gantry milling machines from France's Forest Line. Among them, Remele has up to 6 sets, the spindle power is 40kW, the speed is 40,000r/min, and the wall thickness of the machined parts is as thin as 0.76mm. At the same time, it also has a Fischer machine head with a spindle power of 75kW and a speed of 5000r/min. It can process large-sized wing panels and has high cutting efficiency. Bell Helicopter also added the Automax IV dual-spindle 5-axis high-speed machining center for processing aircraft structural parts from Marwin, Philadelphia, USA. The specification is 20m×8m×9m, the spindle speed is 24000r/min, and the feed speed is m20m/min.

2 High-efficiency CNC machining The application of CNC technology in aircraft manufacturing companies in developed countries is high. Performance: not only the high utilization rate of CNC equipment (generally up to 80%), high spindle utilization rate (95%), and high processing efficiency, short processing cycle, labor productivity is 20 to 40 times that of China. The processing efficiency of the large-scale integrated machining parts is about 50kg/h. McDonnell Douglas manufactures the C-17 military transport aircraft landing gear bay frame with a processing efficiency of approximately 30kg/h. 

3 Widely used advanced CAD/CAPP/CAM system widely used CAD/CAPP/CAM/CAE automation design and manufacturing application software and parallel engineering such as DFX, and has sufficient process knowledge database, cutting parameter database and various standardized technical materials. Enable tools. Therefore, the design and process methods are advanced, the technology is excellent, the NC processing program is high quality, the process preparation cycle is shortened, the equipment utilization rate and production efficiency are improved, and the parts production cycle is greatly shortened. 

4 DNC technology is widely used Most of the aircraft manufacturing companies in developed countries have widely used distributed digital control technology (Distributed NC, DNC) in the late 1970s and 1980s. Boeing's DNC system, established in the Wichita military division, is connected to more than 130 CNC equipment distributed in several different workshops, including machining centers, large milling machines, and CNC measuring machines. The McDonnell Douglas, MBB and extron plants have established DNC systems. There are about 20,000 small aircraft parts subcontract manufacturers in the United States, and 60% to 80% use the DNC system. The use of DNC technology has obvious economic and technical benefits, usually increasing productivity by 15% to 20%. 

5 Application of High Speed ​​Machining Technology High Speed ​​Machining (HSM) is considered to be the most important means in the 21st century machining process. High-speed cutting has obvious advantages over conventional cutting: machining time is reduced by about 60% to 80%, feed rate is increased by 5 to 10 times, material removal rate is increased by 3 to 5 times, tool durability is increased by 70%, and cutting force is reduced by about 30%, surface roughness Ramax can reach 8 ~ 10μm, workpiece temperature rise is low, thermal deformation, thermal expansion is reduced, suitable for processing slender, complex thin-walled parts.
The use of high-speed CNC machining technology for large and complex integral structural parts of aircraft is a trend in the development of aircraft machining technology in recent years. Therefore, in the mid-to-late 1990s, aircraft manufacturers added many advanced multi-coordinate high-speed CNC milling and machining centers for the processing of various structural parts of aluminum, titanium, steel and other materials. Boeing Bertsche Engineering's high-speed machining center for the machining of aerospace aluminum alloy and composite parts.
For high-speed machining of aluminum alloy, the cutting speed can reach 2000-5000m/min, the spindle speed reaches 10000~40000r/min, the machining feed rate is 2~20m/min, and the material removal rate is 30~40kg/h. 
High-speed machining technology puts higher demands on machine tools, tools, control systems, and programming. The research and application of supporting technology for high-speed machining in developed countries is regarded as a systematic project, which is well solved and is constantly improving. 

6 Application of high-automated manufacturing systems Aircraft manufacturing companies in developed countries attach great importance to the application of high-automation manufacturing systems, improve the production capacity of new aircraft, and strengthen the competitiveness of enterprises. In the late 1970s and 1980s, the flexible manufacturing system (FMS) was established for the flexible processing of aircraft structural parts, which played an important role in the development of new machines. In the mid-to-late 1990s, due to the development and advancement of high-speed cutting machine tool technology, the number of aircraft integrated parts increased, and the flexible processing unit or flexible processing unit was used to process the whole structural parts of the aircraft (in the automotive industry). Also get the application). For example, the Boeing Wichita Military Division uses a flexible processing line consisting of high-speed machining units to process the entire frame parts of the aircraft. Dassault Aircraft has also established a flexible processing line in the manufacture of the "Gust" aircraft. It consists of four 5-axis cutting centers, equipped with automated workpiece loading and unloading trolleys, and a robotic-controlled tool library with a capacity of 1000. operator.
Western developed countries not only pay attention to the development of CNC main technology, but also focus on the coordinated development of various unit automation technologies supporting CNC technology, including CNC shop information management system, which enables CNC technology to develop rapidly and reach a high level of application, effectively promoting The development and progress of the aircraft manufacturing industry. At present, aircraft manufacturers in developed countries not only achieve high-efficiency CNC machining, but also realize digital design (DD) and digital manufacturing (DM).

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