This paper covers the topic which includes the development of a 3D printed prototype mould for small-batch injection moulding. There is a tendency for increasingly rapid product development and their testing and certification, which creates a demand for manufacturing products similar to those from later large-scale production. This is achieved by using hybrid tools that contain polymer mould inserts embedded within conventional mould housings. This paper presents all the possibilities and advantages of Rapid Tooling, how it is achieved and what all constructors should pay attention to when developing such tools. The numerical calculation of the mould greatly helps in the development of the tool. The paper includes numerical calculation of the injection moulding process, which gives the part warpage results and calculates the thermal and mechanical loads of the mould inserts. They serve as input data in the numerical calculation for structural analysis of the mould, which gives the results of mould inserts deformations and stress, which are used to calculate their durability. The numerical calculation of the 3D printed mould is followed by the numerical calculation of the traditional steel mould to show the differences between the development and manufacturing conditions of such tools. Then, the polymer mould inserts were manufactured by Fused Filament Fabrication and PolyJet technologies. Their evaluation was made from the aspect of dimension accuracy which was realized by 3D scanning. Finally, conclusions were made based on the results of numerical calculations and the evaluation of 3D printed mould inserts.