| 摘要 |
PURPOSE:To obtain a casting having excellent surface flatness and good finishing accuracy by arranging small side of grain size to wall face side in a cavity and large side of grain side of grain size to inner side in the cavity in polystyrene grains having two kinds of large and small grain sizes. CONSTITUTION:By applying vibration to a forming die 5, in which both polystyrene grains 1, 1..., 2, 2... are packed, the non-forming polystyrene grains 1, 1... having small grain size, which are not yet foamed, is settled to lower side in the inner wall of the cavity 6 and the polystyrene grains 2, 2... having large grain size are piled on the above grains 1, 1.... After that, by blowing the heated steam set the prescribed temp. from many fine holes 8, 8... in the forming die 5, the polystyrene grains 1, 1..., 2, 2... are heated and foamed. By this method, an expendable pattern 9 having excellent flatness on the one side face is obtd. |
