Injection molding is one of most widely-used polymer processing technologies in which hot polymer fills a mold cavity, and is solidified during the subsequent cooling process. In the mold filling stage, the mold temperature should be high to improve flow characteristics, and low to reduce cooling time during the cooling stage. To fulfill these objectives, rapid mold heating technology has been developed to raise mold temperature, without significant increase in cycle time. While the conventional rapid heating technologies required dedicated facilities such as steam heating or high-frequency induction heating system and has a limitation in uniform heating, the purpose of this study was to develop a facile and conformal mold heating unit that uses a carbon nanotube (CNT) film heater. The CNT film heater was used to heat a curved mold with high temperature uniformity, by maintaining uniform distance from the mold surface. The developed conformal heating technology was then applied to a singly curved mold and a multiply curved mold. Considering that the resulting temperature uniformity is superior to the conventional oil heating, the conformal mold heating technology using the CNT film heater can be used to improve part quality and productivity in various molding processes.

The purpose of this study was to develop an efficient mold heating technology by an embedded heating unit. To localize the heating effect in the mold core and prevent heat transfer to surrounding mold plates, the core module with embedded heating unit was assembled to a mold plate in a detachable manner. The detachable core module was then separated from the mold plate when the mold was opened, and thus could be rapidly heated by the embedded heater. The heated core contacted with the mold plate when the mold was closed, and could be cooled by heat conduction to the mold plate of which thermal inertia was much larger than that of the core module. To verify thermal efficiency of the proposed structure, heat transfer simulation was performed with an experimental validation. Mold filling simulation was also performed to investigate the effect of mold heating on improving flow characteristics through a thin and narrow channel. Injection molding experiments were also conducted by adopting the proposed embedded heating module.