Mechnical Design Systems Laboratory, Hiroshima University

Large parts in, for example, construction machineries, are often made by the casting using a sand mold. Sand mold production requires a lot of manual labor, especially for large parts. In addition, since a sand mold must be destroyed to remove the casting from the sand, patterns, from which a mold cavity is created, must be stored in a warehouse to manufacture spare parts in future. To reduce its space and cost, and to automate the construction of a sand casting mold, direct machining of a sand casting mold based on a virtual model of patterns has been studied. Robotic machining of a sand mold seems promising, due to its lower machine cost than machine tools, and lower material cost and higher manufacturing efficiency than the additive manufacturing. However, the robotic milling requires a solution to the problem of poor positioning accuracy of robots. Our research group has proposed a new kinematic model containing the angular positioning error of all six axes, as well as the Denavit- Hartenberg(D-H) errors. Based on this model, the final goal of this study is to apply the error correction to a sand mold machining robot and to improve its positioning accuracy to meet the geometric accuracy requirement for a sand casting mold. To this goal, this paper presents the experimental identification of the present model, and static and dynamic tests to investigate the contouring accuracy, without performing actual machining, under the compensation by the present model.

Keywords: Robot, Machining, Kinematic model