Towards a tolerance representation model for generating tolerance specification schemes and corresponding tolerance zones

Abstract

In this paper, a tolerance representation model for generating tolerance specification schemes and corresponding tolerance zones is proposed to meet the requirement of the representation of tolerance information semantics. This model is hierarchically organized and consists of five layers. They are component, geometric feature, variational geometric constraint, tolerance specification scheme, and tolerance zone layers. The mating relations between components in the component layer, the mating relations between geometric features in the geometric feature layer, the variational geometric constraints between geometric features in the variational geometric constraint layer, the tolerance specification schemes of component in the tolerance specification scheme layer, and the tolerance zones of tolerance specification schemes in the tolerance zone layer are formally defined by one or more adjacency matrices, respectively. Based on the model, a method for generating tolerance specification schemes for component and their resultant tolerance zones is designed. This method shows how to adopt a top-down strategy to carry out tolerance specification for an arbitrary assembly designed in a CAD system. The paper also provides a practical example to illustrate how the method works.

Optimization Method of Assembly Tolerance Types Based on Degree of Freedom

“…In terms of automatic generation of tolerance types, many researchers have conducted a lot of research and summarized it into four categories: Technology and topology related surface (TTRS) based methods [24], assembly positioning constraint-based methods [25][26][27][28], case-based learning methods [29][30][31], and rule-based reasoning methods [8][9][10][11][12][13][14][15][16][32][33][34].…”

“…Rule-based reasoning method [8][9][10][11][12][13][14][15][16][33][34][35]. Zhang [8], Qin [9] and others introduced the theory of polychromatic sets to describe the assembly relationships, constraint types and assembly feature characteristics between parts.…”

“…At present, with the development of digital and intelligent product design, the automatic generation of tolerance specifications has become an important research content and made an important breakthrough. The multi-color set method [8,9], hierarchical tolerance information model method [10][11][12][13][14], adjacency matrix method [15,16] and other methods [17] are combined with the computer to realize automatic reasoning of tolerance types of assembly parts. With the above method of automatic generation of tolerance types, the assembly features of the part are analyzed in order to obtain all the tolerance terms matching the assembly features.…”

A computer-aided tolerance specification method based on multiple attributes decision-making

“…Cao [19] applied graph theory to develop the positioning table method. Qin [20] introduced a top-down strategy to carry out tolerance specification for an arbitrary assembly designed in a Computer-Aided Design (CAD) system. The empirical knowledge can also be useful.…”