Aircraft assembly is the process of combining and connecting aircraft parts or components according to the design and technical requirements to form a higher-level assembly or complete machine based on the principle of size coordination. The needs of society, market competition and the continuous development of related technologies are driving the evolution of aircraft assembly technology to a higher level. So far, aircraft assembly technology has experienced a development process from manual assembly, semi-automated assembly to automated assembly. At present, the rapid development of flexible assembly pushes automated assembly technology to an aircraft assembly technology that has gone from manual assembly to semi-automated assembly. In the course of the development of automated assembly, the rapid development of flexible assembly has pushed automated assembly technology to a new level.

      The development status of foreign advanced assembly technology

      In the past 10 years or so, foreign aircraft assembly technology has developed rapidly. New military and civil aircraft represented by B777, A340, A380, F-22, F-35, etc. reflect the current status and development trend of foreign aircraft manufacturing technology. Technically based on the digital size coordination system of a single product data source, implement digital size engineering technology, realize assembly process optimization through assembly simulation, apply flexible and modular tooling technology, processing and inspection units and integrate them into a series of automated assembly systems For the automated assembly of the airframe structure, a large number of meters used long-life connection technology to realize the high-quality and high-efficiency assembly of the long-life aircraft structure. The following introduces foreign advanced assembly technology from the aspects of automatic assembly tooling, automatic assembly unit, automatic assembly system, automatic hole making, automatic drilling and riveting, assembly inspection, and digital assembly management technology.

1. Automated assembly tooling technology

Different from traditional assembly tooling, foreign assembly tooling has been developed into CNC automated tooling, mainly including in-line flexible assembly tooling, multi-point forming vacuum suction cup flexible assembly tooling, decentralized fuselage flexible assembly tooling, automatic docking flat assembly, etc. , They have the characteristics of modularization, digitization and automation.

(1) Determinant flexible assembly tooling

Determinant flexible assembly tooling includes wall panel tooling and spar tooling. The former is used to assemble the wing panels of the Airbus series of civil aircraft, and the latter is used to assemble the wing spars of Boeing aircraft such as B-737, B-777, and C-17. Airbus wing panel flexible assembly tooling can complete the assembly of the wing panel of A330/340, A319/320/321/A300 series aircraft. The latest A380 aircraft also uses this type of assembly tooling.

(2) Multi-lattice forming vacuum suction cup flexible assembly tooling

Multi-lattice forming vacuum suction cup flexible assembly tooling is composed of a set of column suction cups. The suction cups can be moved and positioned in three dimensions under program control to generate an evenly distributed suction dot matrix that is fully consistent with the curved surface of the assembly, and can accurately and reliably position and Clamp the siding. When the product shape changes, the adsorption lattice layout is automatically adjusted to adapt to different assembly shapes. Since the early 1990s, this multi-lattice forming vacuum suction cup flexible assembly tooling technology has been widely used in Daimler-Benz Aerospace, Boeing, McDonnell Douglas, Grumman, British Aerospace, CASA, EADS/air In the flexible assembly and production of military and civil aircraft of companies such as passenger and Bombardier Aerospace

(1) Distributed flexible assembly tooling for the fuselage.

      The decentralized fuselage flexible assembly tooling is based on laser tracking and positioning, and is composed of a set of tooling units controlled by CNC, which eliminates the application of traditional large-scale assembly frames, promotes assembly automation and flexibility, and has simple structure, good openness, It has the advantages of small footprint and reconfigurability, and has been widely used in the assembly and manufacturing of large aircraft fuselages.

(2) Automated docking platform

      The automated docking platform consists of a computer-controlled automated jack (or positioner), a laser measurement system and a platform control system. Compared with the traditional docking platform, the aircraft quality is greatly improved, the efficiency is high, the cycle is short, and the versatility is strong. It can adapt to different sizes of fuselage and wing structures.

2Automated assembly cell technology

      Foreign large-scale civil aircraft structures widely use automated assembly technology, based on technologies such as numerical control tooling, home inspection units, and digital positioning. The processing unit mainly includes hole making unit, hole strengthening unit, automatic glue injection unit, automatic feeding unit, fastener insertion unit, ring and groove nail installation unit, pull nail installation unit, welding unit, etc.; inspection unit includes photo measurement hole positioning unit , Normal detection unit, hole detection unit, etc.

(1) The hole-making unit is used for drilling and countersinking the structure. Hole making unit generally consists of drilling spindle, drill chuck, position feedback linear encoder, servo feed mechanism, safety mechanism and so on.

(2) The hole strengthening unit realizes the extrusion of the hole through the bulging of the mandrel to the slotted bushing, and completes the hole strengthening to improve the fatigue resistance of the connecting hole. The hole strengthening unit is mainly developed by the American Fatigue Technology (FTI) company.

(3) The automatic glue injection unit is used to inject a certain amount of sealant into the hole (from the side of the countersunk socket) before the rivet or bolt is installed. When the glue is injected, the sealant is applied evenly in the hole by rotating.

(4) The automatic feeding unit is used to complete the automatic feeding of fasteners. There are two types: hopper type and box type. The carrying case feeding unit includes several parts such as an offline fastener filling station, a fastener storage box, an automatic feeding device, and a carrying case manual cleaning device. The carrying case feeding unit can complete automatic feeding of headless rivets, ring grooved nails, countersunk rivets, convex rivets and rings.

(5) The fastener insertion unit is used to measure the length of fasteners, insert gap-type fasteners and install interference-type fasteners. The main components of the fastener insertion unit include a feed head for feeding, a cylinder with an encoder, a drive for insertion and installation, etc., through the linear grating encoder (lithography ruler) for axial positioning, and the insertion of the fastener The process is monitored and confirmed, and the length, orientation, diameter, interference level and installation speed of the fastener are fed back in real time.

(6) The riveting unit is divided into three types: traditional hydraulic pressure riveting unit, new electromagnetic riveting unit and electric riveting unit. Yuan power head is light and handy, riveting efficiency is high, riveting amount is even. The electric riveting unit adopts roller screw servo feed technology to realize riveting, which has the characteristics of high precision, high repeatability and no oil pollution.

(7) When the ring groove nail installation unit is used, insert the ring groove nail first, and then automatically install the ring ring on the side of the nail tail and realize the riveting assist electromagnetic riveting technology to realize the automatic installation of the ring ring. This technology is commonly used in Boeing and air Automated assembly of passenger and large civil aircraft wall panels.

(8) The puller nail installation unit is used for the automatic installation of single-threaded puller nails for composite material structures. It has been used in the automated assembly of Airbus aircraft composite flat tails.

(9) The milling unit is used to flatten the formed nail heads of headless rivets, compensation head rivets, crown head rivets, and the protruding parts after installation of single-sided rivets to ensure a good aerodynamic shape of the aircraft.

(10) The welding unit is used for automatic welding and assembly of aircraft metal structures. The advanced technologies currently applied include laser welding and friction stir welding.

(11) The camera inspection unit is used to display, confirm and calibrate the position of the processing point through machine vision.

(12) The normal detection unit uses several eddy current sensors or small laser rangefinders to perform multi-point measurement to determine the normal of the workpiece processing point, and feed it back to the machine tool control system for adjustment to ensure the verticality of the hole.

(13) The hole detection unit uses a probe with a servo drive to measure the diameter and concentricity of the hole. During detection, the proximity switch is used to prevent collisions and protect the wall panels or probes from damage. The hole P data is fed back by the machine in order to identify out-of-tolerance conditions.

3 Automated assembly system

      Foreign aircraft automated assembly technology has changed from an automatic drilling and riveting system consisting of a single CNC automatic drilling and riveting machine and a CNC bracket to a flexible assembly tooling, modular processing units, CNC positioning systems (including robots), automatic feeding systems and digital inspections. The development of flexible assembly systems composed of systems. The flexible assembly system mainly includes the wing panel flexible assembly system, the spar flexible assembly system, the composite tail flexible assembly system, the fuselage panel flexible assembly system, the robot flexible assembly system, the fuselage ring riveting automatic assembly system and the automatic docking platform Wait.

(1) The flexible panel assembly system has been widely used in the assembly of Airbus series aircraft wing panels. The flexible spar assembly system has been used in the automated assembly of most large components of Boeing civil aircraft spars. It integrates electromagnetic riveting technology and sports yoke assembly and technology. Its latest development is E500 (ASAT4)C -17 The fourth-generation automated spar flexible assembly system. The most notable feature of the above-mentioned flexible assembly system is the use of electromagnetic riveting power head and determinant high-speed column array flexible assembly tooling, which can adapt to the flexible assembly of different specifications and sizes of wall panels or spars.

(2) The fuselage wall panel developed by the German company BROTJE uses automatic ring riveting technology, which has been applied to the fuselage wall panel of A380, B-737, C-17 and other aircraft.

(3) The composite elevator flexible assembly system can complete the measurement and calibration of the trailing edge, wall panel drilling and countersinking, rivet selection and supply, glue injection, riveting, wall panel surface waviness measurement and other processes.

(4) EI and Airbus UK jointly developed a robot flexible assembly system for the assembly of wing panels and skeletons. The main functions of the system include: pressing wall panels, wall panel thickness measurement, drilling, detection, insertion, bolts and ring groove nails and installation. The company has developed a set of Tricept805 virtual axis robots for automated assembly of A380 tail torque boxes. Assembly system (hole making and installation single-sided fastening, etc.). Germany has developed a robotic assembly system for the assembly of composite airframes.

4Automatic hole making technology

Modern aircraft structures use a large number of difficult-to-process materials such as composite materials and titanium alloys. Large aircraft also have higher requirements for the preparation accuracy of large-size holes. Therefore, automated flexible hole-making technology is generally used to meet the long life and stealth structure of the structure. , Interchangeability requirements. The automatic hole making system includes the cabin floor hole making system, the wing wall hole making system, the long string flexible hole making system, the flexible tracking hole making unit, the small mobile automatic hole making unit, and the robot hole making system.

5Automatic drilling and riveting technology

Automatic drilling and riveting technology has been widely adopted since the 1970s. At present, foreign aircraft manufacturers still have considerable assembly work done by conventional hydraulic-powered automatic drilling and riveting machines equipped with semi-automatic or fully automatic brackets. GEMCOR Also developed a fully electric riveting, which relies on the electric roller screw linear power head to provide pressure to complete the riveting. Replacing hydraulic riveting with all-electric riveting has become the development trend of automatic drilling and riveting machines.

6 Advanced inspection and test technology for assembly

At present, foreign countries have adopted technologies such as laser tracking and positioning and geometric size inspection, automated non-destructive inspection of composite material assemblies, infrared photographic inspection, and advanced leak inspection of aircraft sealing structures in assembly inspection and testing.

Suggestions for the development of domestic aircraft assembly technology

In order to ensure the quality of the connection, increase the body's fatigue life, and increase production efficiency, foreign military and civilian aircraft generally use automated assembly technology, but when automation is difficult to achieve, some manual assembly is used.

According to the development status of domestic aircraft assembly technology, and with reference to the overall application status of foreign military and civil aircraft automated assembly technology, we put forward suggestions for the development of domestic aircraft assembly technology:

(1) Actively organize the development and configuration of the automatic bracket system, strengthen the research of automatic drilling and riveting technology, and improve the application level of automatic drilling and riveting equipment.

(2) Development of flexible assembly technology, including:

Flexible assembly tooling technology

Automated processing cell technology

Assembly automation testing technology;

Automatic assembly system integration technology;

Assembly digital positioning technology

Digital assembly process planning technology

(3) Focusing on domestic research and development, combined with the introduction of foreign advanced technology, realize the localization of flexible assembly tooling, processing units and inspection units to meet the large demand of domestic aviation factories for aircraft flexible assembly systems.