# Optimization Method of Assembly Tolerance Types Based on Degree of Freedom
## 8 Conclusions  
The method of optimizing tolerance types using the DOF of the tolerance zone has a theoretical basis. This article analyzes the influence of the displacement of the assembly contact surface on the geometric tolerance of the assembly, and obtains the CPDF. It can be considered a sensitive factor in assembly tolerance analysis. In order to facilitate the optimization of tolerance types for the assembly feature surfaces of parts through the tolerance zone degrees of freedom, an algorithm flow for selecting tolerance types, the DOF of the tolerance zone vectors, and CPDF vectors was constructed using the Boolean operation relationship between vector sets. The example verifies the feasibility of the preferred model of assembly body shape and position tolerance elements based on the DOF of the tolerance zone. The algorithmic process of selecting tolerance types using the DOF of the tolerance zone and CPDF can improve the automatic generation method of tolerance specifications based on rule-based reasoning. The new method can reduce the number of recommended tolerances and the difficulty of designers' decision making: for example, in combination with [PERSON]'s [33] method, the number of tolerance types is reduced from eight to five. At the same time, it can ensure that the selection of tolerance types meets the geometric functional requirements of assemblies: for example, there will not be a single circularity or straightness item to control the shape tolerance, and there will not be a combination of circularity and straightness selected to control the shape tolerance. The method proposed in this article has practical application value in the tolerance design of mechanical products, and this example can serve as a simplified model for a simple stamping machine, providing reference for practical applications. However, in terms of the breadth of the research, there are some limitations in the application scope, as shown in the process of using Boolean operations to find CPDFs, where they are only used for the geometric function requirements of components with a single benchmark. The future research direction will explore how to use the DOF vector to derive the CPDF for assembly under multiple benchmarks, and complete the tolerance specification design of high-precision mechanical products with multiple degrees of freedom [43,44]; Additionally, future research will explore how to use ontology technology to achieve intelligent screening and improve design efficiency. Conceptualization, G.L. and M.H. ; methodology, G.L. ; validation, G.L., L.C. and M.H. ; formal analysis, G.L. ; investigation, G.L. ; resources, L.C. ; data curation, G.L. ; writing--original draft preparation, G.L. ; writing--review and editing, G.L. and M.H. ; visualization, M.H. ; supervision, L.C. ; project administration, G.L. ; funding acquisition, M.H. And G.L. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Natural Science Foundation of China (No. 52165064) and was supported by the Project on Enhancement of Basic Research Ability of Young and Middle-aged Teachers in Universities and Colleges of Guangxi (No.20020 KY31008). The APC was funded by the National Natural Science Foundation of China. Not applicable.