MANUFACTURE OF LOST PATTERN FOR CASTING

PURPOSE:To provide a manufacturing method of a lost pattern for casting excellent in surface condition and dimensional accuracy at excellent productivity. CONSTITUTION:Into a forming mold for pattern, foaming synthetic resin beads and the suitable low m.p. grains are mixed and filled. In such a mixed material, the beads are foamed and expanded by heating and become the mutually fused synthetic resin foam body 1' and at the same time, the low m.p. grains are melted and filled up as the low m.p. material 2' at gap of slit, etc., among the mutually fused synthetic resin foam bodies. In such a condition, by cooling and opening the die, the lost pattern 5 for casting excellent in flat surface condition without damaging the dimensional accuracy is obtd.