Development of a Computer-Aided Tolerancing System in CAD Environment

Although mechanical designers can take the advantage of computer-aided tools to assist their tasks, yet tolerance design is still based on experience or trial and error methods. This paper is an effort to develop a computer-aided tolerancing system with systematic analysis in a CAD (Computer-Aided Design) environment. The developed software contains a geometric dimensioning and tolerancing (GD&T) database and five major modules that are (1) feature extraction module, (2) GD&T specification extraction module, (3) fitting assignment module, (4) tolerance network construction module, and (5) interface for tolerance analysis. The developed system assists the designer to evaluate tolerance accumulation of an assembly that provides a reference for tolerance refinement. The spindle assembly of a CNC turning center is also used as an example to illustrate the tolerancing system.