Conformal Mold Heating and Cooling Using a Carbon Nanotube Film Heater and Additively Manufactured Cellular Metamaterial

In injection molding, the mold temperature needs to be controlled carefully not only to improve part quality but also to reduce cycle time. To fulfill these objectives, an energy-efficient mold heating and cooling technology is proposed to obtain conformal temperature control of mold surfaces. For conformal mold heating, a carbon nanotube (CNT) film heater was prepared and installed in a curved mold by maintaining a uniform distance from the mold surface, and its conformal heating capability was investigated numerically and experimentally. To improve the heating capability by preventing energy loss, an additively manufactured cellular metamaterial was placed beneath the CNT film heater, which played the role of a thermal insulator. For conformal and rapid mold cooling, this cellular metamaterial acts as a heat exchanger by circulating a coolant through the porous space of the cellular structure. The combinational use of the CNT film heater and cellular metamaterial ensures uniform temperature change on the mold surface during the thermal cycle by maintaining the temperature deviation within ± 6 °C during the heating stage and ± 0.3 °C during the cooling stage. Considering that this temperature uniformity is superior to the previous mold heating technologies, such as steam or induction heating, the proposed conformal mold heating and cooling technology can be used to improve part quality and productivity in various molding processes.