The doctoral thesis theme relates to the technology of hybrid manufacturing of tooling inserts intended for injection moulding of polymers. In this case hybrid manufacturing means the combination of two technologies, a modern additive technology where the material is added in layers and a conventional cutting technology. This thesis deals with automatic splitting of injection moulding tooling inserts into two parts: the part most suitable for manufacturing with cutting technologies and the part that can only be manufactured with additive technologies. For this purpose, a splitting criteria was defined and a software that analyses the CAD model and automatically defines the splitting plane was developed. It is assumed that the inlet and outlet cooling channels of the tooling insert in question are either on the bottom or the side surface of the injection moulding tooling insert. The splitting criteria was confirmed on a real industrial case of manufacturing a tooling insert for injection moulding of a product, which is used in pharmacy. Simulations and measurements of the temperature field while cooling the injection moulding tooling inserts showed a significantly faster and evenly distributed cooling effect. Furthermore, the hybrid manufacturing method yielded a 51% and 48% decrease in production time and cost, respectively, in comparison with the additive technology.