In polymer injection moulding the barrel head incorporates the flow transition from the barrel into the nozzle. The contour of this connection to the nozzle must be streamlined to avoid hang-up of the material and should utilize forced purging of this section. However, in literature only a limited amount of work is found on the design of the flow domain in this area. In the concrete work a numerical study is used to investigate, the effect of transition radii and opening angle of the conical-shaped transition region regarding pressure loss, viscous heating, shear rates and wall shear stress. The numerical simulation is performed for different polymeric materials, barrel diameters and inject volume flow rates. To reduce the computational costs of the CFD simulation the flow is regarded as steady-state and incompressible. Moreover, the flow domain is rotational symmetric, leading to a 2D velocity field. The study is performed by means of the CAD and CFD automation software CAESES and an extended version of the open source CFD package OpenFOAM. It is shown, that depending on opening angle and transition radius between cone and nozzle very high shear rates and wall shear stresses may occur in this area of the barrel head. For a fixed cone opening angle and die diameter it is possible to find an optimum transition radius cone-nozzle, independent of flow rate and barrel diameter.