Study On Clamping Optimization Of Flexible Fixture For Aircraft Skin Trimming Process

The new generation of flexible fixture has been regarded as one of themain development tendencies of tooling and fixture since it has goodadaptability for parts with different shapes and different curvature, and alsocan reach high machining accuracy due to its joint property and cushioning.The aircraft skin, as thin-wall aluminum-alloy parts, is easy to deformduring trimming or other cutting process. Usually sufficient and equallydistributed fixtures and supports are adopted under the machining part toguarantee the machining accuracy, but such method takes a lot of time andfixture resource.In this thesis, the factors inducing elastic deformation during theaircraft skin trimming process with flexible fixture are studied.Optimization scheme based on genetic algorithm is presented to balancethe fixture layout and clamping force to minimize the process deformation.The following contents are discussed:Firstly, an experiencing trimming force model for thin-wall parts isestablished through a series of orthogonal tests, where method of leastsquare is adopted to get the regressive model.Secondly, according to the characteristics of flexible fixture, theaffection to the part elastic deformation during the trimming process forthree main factors is studied and compared through Single-factorexperiments. Commercial FEM software HyperWorks is used to computethe deformation of aircraft skin, which is verified by the experimentalresults. Then the variable domain for the final optimization is defined andthe number of the fixture supports is gotten.Thirdly, the FEM simulation process is simplified by using the HyperWorks CAE process automation tools based on Tcl/Tk technique,and the GA algorithm is actualized by Matlab software, and then the FEMcomputation and optimization is combined to get the minimum processingmax-displacement. From such scheme, the layout of the flexible fixture forthe aircraft skin trimming is finally optimized.