Study On The Methodology Of Concurrent Tolerancing In Design And Manufacturing

Tolerance design affects functional roles and manufacturing costs of products. It has been become a key technique and choke point of information integration in CAD/CAM. On the basis of summarizing current research situations and developments in tolerancing both of abroad and at home, this thesis aims to solve the problem currently unsolved that assembly tolerances and process tolerances cannot be concurrently designed. Further researches on key theories and methods related to concurrent tolerancing are made. The main contents and creative points are as follows. A hierarchical spatial representation model is proposed for design and manufacturing in concurrent tolerance design. Through using of degree of freedom and tolerance zone of a feature, Assembly model is established to present fit feature, component feature, assembly geometric relation, assembly dimension, assembly tolerance, and assembly datum, etc. Component CAPP model is established to present component design feature, component manufacturing feature, geometric relation between features, dimension relations of component, tolerance relations of component, and datum, etc. The correlation matrix between assembly dimension and tolerance, the correlation magnitude matrix between process dimension and tolerance, and the correlation matrix between controlled tolerance and datum are defined. Appropriate algorithms are established to generate automatically assembly dimension/tolerance chains and process dimension/tolerance chains for tolerance analysis and synthesis. An engineering example is introduced to test the proposed model. A composite tolerance design method is proposed for dimensional tolerances and geometric tolerances. In terms of the characteristics of different sorts of geometrical tolerance zones, in one-dimensional tolerance design, the geometrical tolerance with fixed position zones are transformed into equivalent linear dimensional tolerances and the others are treated as additional tolerance constraints. In two-dimensional and three-dimensional tolerance design, the tolerance zones are directly summed up graphically because of the complexity of tolerance interaction. One-datum and two-datum model are introduced to sum up different tolerance zones. An engineering example is introduced to test the method.A systematic method is proposed to present a concurrent composite optimization model based on process capabilities. According to actual distribution of dimensional tolerance, angular tolerance, and geometrical tolerance, the process capability index is used to evaluate the actual process capability of machining operation. From product assembly tolerance design to process tolerance design, optimization design model is presented to directly allocate assembly tolerances into optimal process tolerance through using of pertinent component process planning in concurrent design environment. An example is introduced to test the method. Optimization method of sequential tolerance design is proposed for 3 dimensional part manufacturing. At a stage when some machining operations are finished, the measurement data are used to dynamically allocate unfinished process dimensions and tolerances in an optimal way. An engineering example is used to validate the efficiency of the method. The quality loss function in terms of process tolerances with multiple correlated assembly functional dimensions is proposed in concurrent design environment. A concurrent optimization model in support of minimum manufacturing costs and quality loss with multiple correlated assembly functional dimensions is given. An example is applied to test the method and the results are explained. The prototype system for modeling and representation of tolerance information is given. An engineering example is studied to demonstrate the theory of this dissertation. This thesis is financially supported by National Science Foundation of China, named "Research on the Tolerance Theories and Methods of Micro Components"(No.59975034) and Guangxi Education Office Foundation, named ?...