The injection blow moulding single stage process consists of producing hollow parts starting from the injection moulding of the preform shortly followed by the blow moulding of this preform. Such a process is usually available on dedicated machinery. An innovativ technology allow one to produce hollow parts on a standard injection moulding machine. Both the injection moulding stage and the blow moulding stage are being taken care of in an injection mould. Thus the dimensions of this mould are those of a conventional injection moulding mould. The fact that the two stages are located in the same mould leads to a process more constrained than the conventional one. This process introduces temperature gradients, molecular orientation, high stretch rates and high cooling rates. These constraints lead to a small processing window. In practice, the preform has to remain sufficiently melted to be blown so that the process takes place between the melting temperature and the crystallization temperature. In our numerical approach, the polymer is supposed to be blown in its molten state. Hence we identified the mechanical behaviour of the polymer in its molten state through dynamical rheology experiments. The validity of such an approach remains on the hypothesis that the crystallization does not occur before and during the blow moulding stage. To ensure this assumption, the effects of the cooling rate and the shear rate have been investigated. A viscous Cross model has been proved to be relevant to the problem. Thermal dependence is assumed by an Arrhenius law. The process is simulated through a finite element code (POLYFLOW software) in the Ansys Workbench framework. Thickness measurements using image analysis of tomography data are performed and comparisons with the simulation results show good agreements.