Behaviors of sand flow in flask for the expendable pattern casting process

Tzay Yuan Jang, Teng Shih Shih, Shu San Hsiau

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In the expendable pattern casting (EPC) molding process, sands were properly transported and compacted around the coated patterns by means of vibration. Difficulty arose for the case when it was necessary to transport molding sands into long horizontal cavities to form sand cores. The significant resistance and interlocking among sand particles often cause faults in casting due to incomplete compaction, while an over drastic vibration might cause distortion of the replicas. The behavior of sand motion in flask thus played an important role in designing mold cavities and in making decisions regarding molding conditions. The velocities and directions of sand motion in flask were different from point to point, depending on vibration conditions and the geometry of the flask. As the vibration processed, a layer of sand with a certain thickness near the surface flowed from the center outward to the flask wall, while in the region of 5 to 20 cm beneath surface, sands contracted inward to the center. At further depth, sand settled down steadily to the bottom along the wall. There existed an optimum stratum depth, at which the motion of sand in the horizontal direction approached a maximum value, and thus might meet the needs of sand transported into long cavities. The object of this paper is to investigate the behavior of sand flow in flask. Experimental results indicated that two-dimensional vibration, including the vertical direction, at resonance frequencies might greatly increase the fluidity of sand. The strength of sand flow depended on the acceleration level and the frequencies of the vibration system. With 2- and/or 3-dimensional vibration with sufficiently large gaps between sand and flask wall, air may be entrapped and form bubbles, these bubbles fluctuating drastically in the region near the free surface and blast out. The formation of bubbling is described in this paper.

Original languageEnglish
Pages (from-to)335-343
Number of pages9
JournalJournal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao
Issue number4
StatePublished - 1999


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