3D Tolerance Analysis Methods Based On DP-SDT Deviation Synthetic Theory

Tolerance analysis is an important quality analysis and prediction method using the tolerances and geometric information during the phase of product design. Designers can identify the potential quality defect, improve the tolerance design, reduce the engineering change, reduce the time, and balance the product quality and cost. As the tolerance analysis method is usually very complex, most of the current methods aims at special tolerances and quality requirements, and is insufficient to integrate different assembly information. Taking 3D tolerance analysis as the research object, this thesis studies on deviation synthesis method, tolerance modeling, quality modeling, and Computer-Aided Tolerancing (CAT). The details are as follows.This thesis proposes a new DP-SDT deviation synthetic theory. Firstly, the thesis construct the overall solution of DP-SDT deviaiton synthesis based on the small displacement torsor (SDT) model and deviaiton propagation and accumulation analysis method (DP). In this solution, we have defined the key features and key parts, assembling process information model, and designed the DP-SDT deviation synthetic solving algorithm based on the independent deviaotns and related deviations. DP-SDT deviation synthetic theory can realize to solve all the feature deviations in the assmlby according to the deviation sources, geometric information, and assembly process information. Meanwhile, the analysis result is more reliable for the theory can better discribe the assembly process information using the assembly sequence, locating modes, fit modes, and fixture information.This thesis proposes a new tolerance analysis method for assembling process based on DP-SDT theory. The theory takes DP-SDT deviation synthetic theory as the main algorithm, and constructs the models and solving algorithms of feature tolerance deviations, locating deviations, form deviations according to tolerance classification according to the action modes in DP-SDT theory. Then the method constructs 5 kinds of quality requirement models like dimensional requirements and geometric requirememnts etc., and predict the quality according to defection and tolerance contributions etc. DP-SDT tolerance analysis method realizes to predict, evaluate the product quality according to 3D dimensional tolerances, geometric tolerances, geometric information, and various kinds of assembly process information. A case study on the tolerance optimization project of the stator-core lamination assembling is provided to verify the performacen of the DP-SDT tolerance analysis method.This thesis proposes a new trajectory deviation analysis method based on DP-SDT theory for the product using process. The method analyzes the trajectory deviation of the quality point under the motion displacement, forced direction, vibration, geometric information, assembly process information, and tolerances based on DP-SDT tolerance analysis method for assembling process. In this method, motion displacement is integrated using a "direction and location transformation of motion groups with multi-nodes" and motion displacement deviation solving algorithm, and forced direction and vibration are integrated using a "search algorithm of locating parameters". DP-SDT trajectory deviation analysis method discribes the product quality in 4 ways, such as integrated trajectory deviations and trajectory idle stroke etc. DP-SDT trajectory deviation analysis method for product operation process increases the application area of tolerance analysis method. This method can simulate and predict the product operating quality to a certain extent, and provide a more comprehensive tolerance optimization scheme. A cace study on tolerance optimization problem of a railway wheel lathe saddle is provided to verify the performance of the DP-SDT trajectory analysis method.According to the above tolerance analysis methods, this thesis has developed two CAT prototype system respectively. The developed CAT systems can realize to get the geometric information from the CAD system by interaction, define the assembly process information with the help of the operation interface, help to manage the huge data about the tolerances, geometric information, deviations, and assembly process information. And the CAT systems can realize to process the complex algorithms for solving tolerance deviations, solving deviation synthesis, solving quality requirements in background process, which can greatly simplify the tolerance analysis and optimization process. A cace study on the tolerance analysis and trajectory analysis of the lathe tool in a lathe saddle is provided to verify the performance of the two CAT prototype systems.