In injection molding, surface defects such as weld-line and silver streaks are serious problems which trouble engineers. It is also known that these surface defects can be prevented by heating the mold cavity surface to above the resin melting point Tm or glass transition point Tg. In this study, we designed and made a rapid heating and cooling mold applying induction heating, which is capable of continuously heating and cooling the cavity surface rapidly. This mold has a cavity insert with coils and cooling channels arranged inside the mold base. Using the mold, heating and cooling molding and normal molding without performing heating and cooling were performed and effects on the external view and surface properties of rapidly heated and cooled molded products were investigated. Observation of the surface of the product molded using this mold showed that in normal molding, the formation of V-shaped weld-lines is seen on the molded product surface. On the other hand, when heating and cooling is performed in molding, no weld-lines are found, and compared to normal molding, a highly glossy molded product surface has been confirmed.
