Tool Path Generation For 2.5D Residual-Area Milling Of Aircraft Structural Parts

Aircraft structural parts are important components of plane body skeleton and aero-dynamic shape so that they are widely used in all kinds of planes. 2.5D parts are in the majority of aircraft structural parts, which are commonly made by CNC machining center. With so many years of development, machining centers are capable of coping with different situations, and how to plan the process efficiently is the key point to improving machining efficiency, because it usually takes too much time to make preparations and program manually. Meanwhile, there will be some residual areas due to the characteristics of the aircraft structural parts and the weakness of the CAM software. Although you can call the CAM software to generate tool path for residual-area again, it usually needs to edit the tool path manually to cover the whole residual-area or the total length of tool path is longer than it should have been. Therefore, the research concerns about how to generate optimum tool path for 2.5D residual-area milling of aircraft structural parts.(1) There are two most popular tool path patterns for 2.5D milling, direction-parallel and contour-parallel. The direction-parallel tool path suffers more cutting time and worse surface quality than that of the contour-parallel tool path in the case of complex shapes, so for complex shapes, the contour-parallel tool path is more usually preferred. But the contour-parallel tool path for residual-area can be shortened by cutting off some unuseful too path curves. Apart from two patterns above, the paper proposed another better way named after domain-divided for some special cases to shorten the total length of tool path.(2) An offset algorithm is important to the tool path generation process. As the offset algorithm provided by CATIA sometimes can’t get the right offset curves, the paper put forward a new offset algorithm based on a 2D point-sequence curve which can avoid the local and global interference. It’s proved to me more stable and efficient.(3) To divide a domain into some sub-domains for generating too path in the next stage, the paper presented a new constraint Delaunay triangulation method, making it possible to divide the residual-area into several reasonable domains automatically. After the tool path for every domain is generated, the integral tool-path will be optimally connected.(4) Based on CATIA secondary development interface(CAA) and Visual Studio 2005, a system named optimum tool path generation for 2.5D residual-area milling of aircraft structural parts was developed using C++ programming language. The system automatically generates an integral optimal tool path covering the whole residual-area according to different types. It proved to be more efficient than that CAM system generates.