| 摘要 |
PROBLEM TO BE SOLVED: To completely eliminate remnant of a low melting point metal (a core metal) on the inner wall surface of the hollow part of a plastic molding, resulting in avoiding the deterioration of the material of the inner wall surface portion of the hollow part of the plastic molding. SOLUTION: This method consists of the execution of a pre-heating process, in which a plastic molding such as an intake manifold 2 and a low melting point metal core are arranged in a high frequency induction heating coil 7 provided in an ethylene glycol liquid 5 so as to be pre-heated up to the temperature just below the melting starting temperature of the low melting point metal core through a high frequency induction heating, and a main heating process, in which the low melting point metal core is mainly heated up to its melting temperature in succession to the preheating process. In the pre-heating process, the front layer temperature and the core part temperature of the low melting point metal core are set to be nearly equal to each other. In the main heating process, the low melting point metal core is melted by slow heating so as to flow the molten metal core out of the opening part of the plastic molding 2.
|
