Tolerance modeling approach to part based on directed graph

In order to represent benchmark, fluctuation trend and fluctuation value of geometric shape and dimension of component, a tolerance modeling approach based on directed graph was presented. A 5-tuple was used to represent meta-tolerance. The construction process of tolerance model was as following: firstly defining the reference frame and Key Features (KFs) related to geometric shape and dimension, then describing tolerance relationship between KFs by directed arc of graph and a unit-vector was utilized to represent fluctuation trend of tolerance. All meta-tolerance models were set up based on directed graph. Then the tolerance model was constructed based on sum operation about graph for all meta-tolerance models. And a tolerance modeling system integrating with CATIA V5 was developed. Finally, the approach was validated by an example.