Automatic Assembly of Checking Fixtures Based on Graph Theory

During researching and developing of checking fixtures for cab and auto-body parts there were some problems such as long production period, high costs and difficulties in final assembly because of the interference between interacted components. In this paper, automatic assembly of checking fixtures based on graph theory was developed. Reverse engineering technology was applied to obtain 3D model of cab and auto-body parts with free-form surface. The calculating algorithms of positions and poses for component model, fixture configurations and fixture elements in virtual cab and auto-body assembly space were discussed. Fixture assembly relationships were defined based on graph theory. Transforming a fixture element from its coordinate system to an assembly space with homogeneous transformation matrix was successfully conducted. Automatic assembly was implemented. The results showed that the proposed design method improved the accuracy and efficiency of checking fixtures and could reduce costs of designing new parts.