When long pipe castings are cast by the evaporative pattern casting process, the collaspsibility of the mold inside the pipe occurs at a high probability. In this study, the compactability of molding sand inside the acrylic pattern placed in the vibration flask was measured. It was found that sufficiently high compactability in the pipe can be obtained. Two kinds of rotary vibrations in opposite directions were attempted at the 40 Hz for 30 s respectively under the conditions in this study, and the pipe casting was cast by the evaporative pattern casting process. Different thickness of the pipe casting caused by the rising of the core was observed even at sufficiently high compaction of the molding sand inside the pipe. In addition, casting defects due to the collaspsibility of the mold were observed by the retention of the thermal decomposition gas in the pipe. These casting defects were found to decrease by the coating of a low permeability coat upwards inside the pipe pattern.
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