Study AndDesignof Top-Down Virtual Assemblysystem

Assembly design is a key link of product manufacturing, and it exerts important influence on the product’s quality, cost and development cycle. In the conceptual design stage of products,virtual assemblytechniqueswill consider some problems about the product’s functional structure, assemblability, assembly sequence, assembly paths and assembly timeand so on.Thus,the product development cycle will be shorted and the production efficiency of enterprises will be improved.The paper aimed atthe drawbacks of present CAD softwares and the existent problems of the bottom-up assembly modeling methods.Research and develop the virtual assembly system that supports top-down assembly modeling techniques According to the theory of top-down design and assembly modeling techniques. Firstly, the paper not only introduces the implication and development situation of the virtual assembly techniques, but also discusses the concept and researchstatusof the top-down design method.According to the thought of the top-down design approach to deeply research the overall functional structureframe for the virtual assembly system, and make a overall planning for developing the system.Secondly, because of the assembly model is the core toimplement the top-down design method, so deeply study the definition, expression and assembly relationsof the product assembly model that supports the top-down design.And according to the thought of the assembly method based on assembly constrainttransform.Put forwardthe assembly associated skeleton model that supports the top-down design, and achieve the description of abstract parts and abstract assembly modeling on the assembly level.The product’s assembly hierarchical structure also can be expressed clearly.Make assembly associated skeleton model as abridge of conveying information,and achieve detailed design of the lowerparts. Lastly,analyze the structure of OBJ graphics files and design the interface thatis able to read OBJ graphics files for the system,which achieved the geometric reconstruction of3D geometric modeland added the assistant control function to achieve human-machine interactionin the system. As a result of the tree view is an important part of the assembly system,so according to the structure of assembly associated skeleton model to design the structure of the tree view.And the tree view will be built more humane because of the achievement of adding, deleting and dragging nodes dynamically.ADO data interface technology is applied to implement the connection between database and system in order to maintain the security of the system data, whichlaid a solid foundation for subsequent top-down virtual assembly systemdesign.