Stability Analysis of the Rapid Heating Multilayer Structure Mold by the Contact Error and Thickness of Layers  
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during the entire molding cycle. In the CIM process, the mold temperature is maintained at a much lower level than the resin's glass transition temperature or melting point, making the production cycle efficient. The low-temperature cavity of the CIM process causes the resin to solidify during the resin injection process and form a frozen layer between the hot polymer melt and the cold cavity surface. That leads to defects, such as weld lines, flow marks, swirl marks, low gloss, and cooling to low reproducibility, in the final molded product [8]. However, in the RHCM process, the cavity surface temperature of the mold is brought to a certain level above the glass transition temperature or melting point of the resin used in the process, and the temperature is maintained as the resin is injected. Once the injection is complete, the heating process ends, and the resin filling the cavity is solidified by rapid cooling. The RHCM process has the advantage of increasing the production cycle's efficiency through rapid heating and cooling. It overcomes the limitations of the CIM process, making it possible to produce high-quality molded products in a short time. In order to implement the RHCM process, which has many advantages in injection molding, methods for rapidly heating and cooling the mold are being actively explored. Rapid mold heating is a critical technology for RHCM. Various heating methods such as infrared heating [9; 10; 11], induction heating [12], high-frequency proximity heating [13], gas heating [14], resistance heating [15; 16; 17], and steam heating [18] have been studied. Among them, resistance heating with cartridge heaters and steam heaters is widely used in the industry. The RHCM process applied in this way is widely used to replace the CIM process in specific industries that require high-gloss, weld line-free products. It is typically used for TV panels, automotive parts, and other exterior parts. Cartridge heating and steam heating methods are widely used but have some limitations. These methods involve heating the entire mold by applying a pipe and cartridge heater inside the mold. Because the heat capacity of the mold is large, it is difficult to immediately and accurately control the temperature of the cavity surface using this heating method. Because of this, there is a time delay in heating the cavity surface, and because the structure of the channel where the pipeline and cartridge heater are applied is heated linearly, the temperature distribution is not uniform. Because of these issues, these methods are mainly used for injection molding large parts such as TV panels and automobile parts. They are unsuitable for producing sophisticated parts containing nano or micro units. Steam heating requires a high-pressure steam generator and boiler as additional equipment and many additional facilities, such as steam supply pipes. In addition, once used, steam has the disadvantage of being difficult to recover, resulting in significant energy waste [2]. Surface heating elements complementing the heating method applied through channels are also being investigated. A mold heating method has been developed using a surface heating element. A thin metal film is employed as a heating layer [19]. Recently, a new rapid surface heater has been generated by CVD coating graphene on a silicon wafer [20]. These surface heating elements attract attention as alternatives to linear heating elements because they provide uniform and stable temperature distribution in the application range. However, in the case of thin metal films, the resistance when applying actual power is so low that a large current is easily applied, which reduces electrical stability and is unsuitable for application to molded products of complex shapes. Surface heating elements using graphene coating are easily produced by coating various shapes.