Research And Development On Assembly Sequence Planning System Based On 3D CAD

With the improvement of the CAD/CAM technology, the proportion of the part design and manufacture to the product lifecycle shrinks continuously. However, assembly planning is still largely done artificially, which becomes the primary obstacle in product development. Assembly sequence planning is a key factor in assembly planning, therefore it is imperative to develop a method for automatic planning of assembly sequence. After comprehensive analysis of the state of art domestic and abroad, the thesis delves into the theory related to assembly sequence planning. In order to reduce the time of assembly sequence planning and meet the application requirements, an assembly sequence planning system is built based on geometry models created via 3DCAD platform. Assembly sequences of subassemblies in hierarchical model are obtained between designer and computer, and assembly sequences of parts in subassemblies are generated automatically by computer. Based on 3D geometry model and according to predefined rules, product can be partitioned to subassemblies between designer and computer. Then the hierarchical model can be generated, whose rationality can be checked by assembly simulation module of the 3D CAD system. Thus assembly sequence of subassemblies can be obtained. The method for obtaining the information of connections between parts is presented using the interface of the platform. A relational model of assembly is employed to characterize the information of parts connections based on graph theory. The interferences between parts while being assembled automatically are acquired by using interference checking module of the CAD platform. According to interference matrixes, the disassembly sequence of parts in subassembly can be generated. So the assembly sequence can be obtained by the contrary disassembly sequence. Thus parts sequences of subassemblies can be automatically planned. Applying the principle of COM and VC++, coding of Subassembly information and interference checking through interface of the platform is fulfilled. Assembly sequence planning system can be realized in terms of the interface between designer and computer. The assembly sequence planning process of gear-box is analyzed with the presented method, and its assembly sequence is planned. This practical use case is given to verify the validity of the system.