The flow and filling behaviour of sand in expendable pattern castings

In the expendable pattern casting (EPC) process, sand was fully transported and compacted around the coated patterns by vibration. Difficulty often arose when it was necessary for sand to be transported into long horizontal channels in order to make complex castings. The significant resistance between the particles and the surface of foam patterns and the interlocking amongst sand particles would obstruct the movement of sand. This causes incompletely filled foam cavities, producing the chance of casting defects. The behaviour of sand motion in the flask therefore played an important role in designing mould cavities. This paper studied experimentally the sand flow in the flask, and the filling efficiency of sand into long horizontal cavities under various vibration conditions. The experiment results indicated that the behaviour of sand flow depended strongly on the depth of the sand bulk, direction of vibration and the exciting level. The response of the flask under resonant state significantly enhanced the fluidity of sand due to the imposition of two-dimensional vibration. Distinct zones and circulation loops of sand flow were generated within the vibrating flask. Sand filling in the cavities at various locations of sand bulk was also measured and discussed.