Research On Robust Tolerancing And Multi-joint Assembly Discrete Tolerance Optimization In Aircraft Manufacturing

Tolerancing is an important part in process planning of aircraft manufacturing. Meanwhile,reasonable tolerancing can assure interchange coordination requirements of aircraft and directlyaffects the assembly yield, manufacturing quality and cost of the aircraft product. Conventionaltolerance design did not consider that tolerances or other design parameters may bring about variationin the manufacturing process. This variation may lead that manufacturing costs, assemblyperformance generate a lot fluctuation, even the loss of assembly function. In addition to, multi-jointassembly is more widely used in aircraft manufacturing connections. As the coordination accuracy ofmulti-joint assembly is associated with the structure type and location of joint, as well as the choice oftolerance fit for joint, its tolerance design is extremely difficult. In the support of National NaturalScience Foundation of China (50905084) and Aeronautical Science Foundation of China(2010ZE52054), robust tolerancing and multi-joint assembly discrete tolerance optimization inaircraft manufacturing have been deeply studied. The main contents and achievements are as follows:The technology of robust tolerancing in aircraft manufacturing is studied. Tolerance feasiblesensitive robust design model is established incorporating minimum sensitivity method and tolerancemodel method in the case of tolerance design variables variation. According to the characteristic thatcost is different when different processing methods are used to process components, this paper adoptthe mixed tolerance-cost model method. Considering the multi-objective optimization problems oftolerance cost function、 assembly tolerance function sensitivity and cost function sensitivityminimizing, this paper use tolerance stratified sequence method to establish the tolerancemulti-objective optimization solution model. finally, the gray coding and decoding binary code ofgenetic algorithm is used, and the penalty function method is used to treat restraint function. Throughthe comparison with the general optimization result, the conclude that the optimized result has a goodrobustness is obtained.The typical manufacturing coordination dimension chain error model of aircraft multi-jointassembly is analyzed based on the abstract linkage mechanism, then the dimension chain equation ofcoaxial and coplanar degree error is obtained. The probability method is used to solve thecomprehensive accumulative error half bandwidth. The discrete tolerance optimization model ofaircraft multi-joint assembly was established, which refer to the influence of the tolerance zone andthe midpoint of tolerance zone on assembly functional requirements. The branch and bound method is used to solve this kind of integer programming problem. The enumeration tree is established whichincludes all the optional discrete tolerance values, and its each node includes the information of thetolerance cost function and assembly function. Branch bound method are adopted to optimize thesolution space of discrete tolerance model, then the program that tolerance continuity optimization iseasy to cause the results not feasible after the roundness is solved.Based on CATIA V5CAA development platform, robust tolerancing module and discretetolerance optimization module of multi-joint assembly in aircraft manufacturing are developed, andby example to verify its feasibility and effectiveness.