The problem of designing an automatic system to hand posts from bulk, to position them precisely and to weld them on findings, such as earrings, has been effectively solved by employing expert system methodologies and graph theory techniques. Design requirements are represented in terms of desired degrees of freedom, desired type of motion, and the complexity of the mechanism in terms of the number of independent loops. The expert system DOMES, Design of Mechanisms by an Expert System, developed at the University of Rhode Island, is employed to identify several kinematic structures of mechanisms which fulfill all requirements. Present semi-automatic systems require an operator to handle and position findings and posts into a welding machine at rates of approximately sixty findings per minute. The developed system handles four hundred findings per minute. Results show that mechanism design techniques based on graph theory and expert systems are powerful tools for creative mechanism design.
In this paper, emphasis is placed on the design of the mechanical system. However, the developed automatic earring-post assembly system includes several other features. A commercially available fusion welding machine is improved to attain rates of fourteen instead of three welds per second, a fifteen ton power press is integrated into the system and appropriate controls are designed and implemented together with light and acoustic sensors to synchronize the power press, the fusion welding equipment, and the post-handling equipment and to monitor system performance on a real-time basis.