During the injection moulding of rubber compounds it is not always possible to achieve automatically high-quality rubber mouldings, i.e. without flash. This paper examines the effects of moulding and gate geometry on the pressure curve in the mould during injection moulding. The pressure curve in the mould cavity and in the runner system significantly influences flash appearance, it is observed that greater moulding thickness and greater dimensions of the runner system result in a lower pressure in the mould. Conversely, especially small dimensions of the point gate have as a consequence very high pressures in the mould which often cause mould opening during the injection phase, flash appearance and mould damage.