| 摘要 |
PURPOSE:To prepare stably a hollow resin product by a lost core method by using a core which is not made of a low m.p. alloy and hardly generates cracks. CONSTITUTION:A core 1 is formed by impregnating a soft porous body 10 with a substance for impregnation liquid at ordinary temp. in a liquid state and solidifying it by cooling and after a molded item with a built-in core 1 is formed by arranging the core in a mold 4, the molded item is heated to ordinary temp. and the impregnating substance is melted to make it flow out from the soft porous body 10 and then, the soft porous body 10 is removed from the molded item. As the stress of expansion when it is frozen is absorbed in the soft porous body, cracks in the impregnating substance in the core 1 can be prevented from developing and the core is prevented from breaking and defects on the surface of the hollow part can be prevented from occurring. |
