Research Of Tolerance Design For Assembly

The phase of tolerance design impacts the assembly of product directly. The tolerance of assembly is accumulated by part tolerance. Computer Aided Tolerancing is a key technology of CAD/CAM integration, which is one of the important factors which affect product quality and cost. If the technology is applied on the product assembly stage ,not only can improve product performance, but also reduce the cost of manufacturing and testing phase. Compared with the traditional assembly, Computer Aided Tolerancing enhances the value of product.From the start with the formation of assembly, the model of assembly dimension chain is builded. Based the assembly information model and assembly feature model , assembly-oriented hierarchical model of the assembly dimension chain is builded. According to the characteristics of the assembly dimension chain, this paper raised the dimension chain data structure. based on the constraint mechanism of Pro/E software platform ,the method of the constraint information and dimensional information were given.The method of automatically generated dimension chain was improved, the system automatically gets the information needed by the user-specified two elements of closed loop . The dimension chain is generated automatically by a certain search algorithm. The method of determining increase or decrease of loop is given, based on vector direction.Based the Comparison of traditional tolerance design method, using Monte Carlo tolerance design method, which could reflect the actual results and processing conditions. We use the method of equal precision in tolerance synthesis. tolerance design system is developed using VS2008 and Pro/TOOLKIT development package .The paper takes a solid assemble as an example to make an verification of the system. The results are saved in the ACCESS database.