Research On Assembly Tolerance Design Based On Pro/E

As an important standard to estimate product's quality, tolerance has great effect on product's assembly feasibility and manufacturability. It also affects weightly product's function and cost. Tolerance design is an important phase in the design of mechanical product, which is a key technology in the integration of CAD and CAM. This paper takes up with the realization of Computer Aided Tolerancing in Pro/E software. It mainly contains:The data structure and information of the assembly model is known well through the analysis of assembly information model in the CAD environment; The assembly database is established for assembly dimension chain. Using the further development tool of Pro/TOOLKIT, some correlative data is extracted from the CAD model and stored in the database, which makes it come true that data is exchanged from three-dimensional CAD model to planar database. The strategy, method and basal course of automatic produce of assembly dimension chain are proposed based on the assembly database.Based on experimental statistical data, three product cost-tolerance model's precision is analyzed with curve fitting by least square method. The manipulative parameters of the cost-tolerance model are presented, which are based on manufacture feature. The concept of quality loss cost is expatiated. Furthermore, the mathematic model of tolerance optimization design is proposed from the point of DFQ (Design for Quality) in this paper. PSO (Particle Swarm Optimization) is used for tolerance optimization, and the method of keeping the swarm's number is used to solve the constraint condition. The feasibility of PSO to solve tolerance optimization problem is proved by the problem of tolerance design of turbine's rotor system. At the same time, the significative effect for product's quality of tolerance optimization design with least total cost is also proved.A tolerance design system is developed on the platform of VC++.net 2003, with Pro/E's further development tool of Pro/TOOLKIT The system can integrate with Pro/E completely. It contains three parts, which are automatic produce of assembly dimension chain, tolerance optimization design and assembly tolerance analysis. The framework of the system is expatiated, and every part's function and use method is described detailedly with the example of turbine's rotor system.