The precise regulation of mold temperatures and flow rates in injection molding is a major prerequisite for the resource-efficient, economical and reliable production of high-quality plastic parts. In order to optimize the design and monitoring of mold temperature control, the real temperatures, pressures and flow rates must be continuously recorded during the injection-molding process. For this purpose, a sensor system is being developed at the Fraunhofer Institute for Surface Engineering and Thin Films IST with which, for the first time, the temperature can be measured directly inside the three-dimensional temperature-control channels.