The objective of this work is to replace laboratory testing of cranial orthosis design by virtual prototyping using numerical modelling and simulation technologies. In this paper, the focus is put on pre-processing stage of the numerical modelling process. In future Computational Structural Dynamics Simulations will be performed during development of new cranial orthosis design at Invent Medical Group (IMG) company. Stiffness of cranial orthosis will be evaluated by means of numerical modelling and simulation and will replace necessity of physical testing of each and every new design of cranial orthosis to ensure its proper behaviour. Objective of this project is to create a semi-automatic system of mesh generation from the input geometric model based on open source software Netgen Mesh Generator. Geometry of the structure as an input file for meshing is provided in STL format. The output of this project is a software tool which will take a geometric model as an input and produce the finite element mesh with all boundary conditions as an output. The mesh produced is then used for calculation of cranial orthosis stiffness using open source code ESPRESO. Simulation results are verified by comparing with results of the same numerical simulation performed using well-established software package ANSYS and with physical experiment as well.