Screening Product Tolerances Considering Semantic Variation Propagation and Fusion for Assembly Precision Analysis

Considering that each computer-aided design (CAD) system has independent geometric dimensioning and tolerancing modeling method, precision information model generated by different CAD systems is difficult to be shared and reused by the downstream precision analysis system. To tackle the problem that tolerance semantic information cannot be transmitted through data exchange standards, this paper aims to propose a novel semantic tolerance screening approach to represent precision information for assembly precision analysis (APA) in the design stage. Based on semantic correlation between tolerance propagation and accumulation, precision information of multi-parts is preliminarily screened out. Then by utilizing semantic web rule language rules to determine the type and position of tolerance zones, multiple tolerances existing on a precision feature surface are refinedly screened out. Finally, a formal tolerance screening ontology, named ToS-Ontology, is generated for performing APA of complex products. The effectiveness of the proposed approach is demonstrated by a practical example, which is to calculate center distance between two holes to ensure bolts can pass smoothly in the limit case.