Recently, the green sand molding processes using compressed air and squeeze are increasingly used in place of the jolt-squeeze molding in view of noise problem, mold accuracy and productivity. These processes are mainly divided into two types; the air- flow + squeeze(flask type) and the blow + squeeze (flaskless type). In the former type, the green sand is dropped into the flask under gravity, after that the compressed air is applied onto the sand layer (air-flow). Squeeze is operated further on the sand. In the latter type, green sand is blown from magazine into cavity using compressed air, and then squeeze is operated. The blow molding is suitable for mass production of small and middle iron castings because of the flaskless process. In the blow stage, the green sand particle is transported into cavity with high speed by air flow and then compacted. The. blow stage is the subject of this study. In the blow molding, green sand particles and air flow interact with each other, resulting in very complex phenomenon. Although many studies have been done, the details have not been clarified on the behavior of green sand particles both experimentally and theoretically. In the present study, the authors try to analyze the movement of the green sand particle using Distinct Element Method (DEM) which is discontinuous model. In this model, the green sand particles are assumed to be viscoelastic materials. The individual particles are moved by the three forces, namely, contact force, drag force and gravitational force. The contact force is calculated from the model using a spring, dash-pot and slider. The drag force is calculated by the analysis of air flow. This model is able to analyze various kinds of sand molding process such as blowing, squeeze and so on. The numerical simulation has been executed to predict the. behavior of the sand panicles for the blow stage before squeeze operation. Furthermore, the laboratory experiments have been carried out to examine the calculated results. The dynamics of green sand particles has been taken by high-speed video camera. From the present simulation, distributions of air flow velocity and par-tiicle movement are obtained to give the insight how the green sand particles are moved from the magazine to cavity and compacted. It is clarified that the contact force when sand panicles are stopped to move in the cavity is much larger than the maximum drag force. From the present study, new useful information and important molding parameters are obtained to determine a reasonable design of blow molding.
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