The quality of the material data measurement is of utmost importance for injection molding simulations as it is fundamental for reliable results. Elastomers consist of at least one rubber polymer, the curing system, reinforcing fillers, processing aids and antiaging agents. Due to its composition various effects occur, like the influence of the curing reaction or the influence of the filler network. Therefore, a process oriented measurement is required. The aim of this master thesis was to determine the viscosity directly on the injection molding machine. For this purpose an existing and an injection molding machine rheometer which was newly developed by DESMA were used. Both machine rheometers were equipped with rectangular slit geometry. To ensure the full comparability of both rheometers they were tested with an ethylene-propylene-dien-termonomer-rubber. The goal was to cover medium to high shear rates. A series of tests were carried out at three different temperatures. Additionally a styrol-butadiene-rubber was characterized with the existing injection molding machine rheometer. During the measurement an increase of temperature was detected in the slit. Therefore a temperature correction is necessary. This requires the measurement of additional rheological and thermal material data like the thermal conductivity, the specific heat capacity, the density and the viscosity determined with the capillary rheometer and the rubber process analyser. A comparison of the temperature in the injection unit with the initial slit temperature showed a huge increase during the injection process due to dissipation. The viscosity values of both rheometers were comparable. But the expected difference of the viscosity levels due to different measurement temperatures could not be proved. A possible explanation is the occurrence of wall slippage effects. The comparison of the viscosity values measured with the capillary rheometer and the injection molding machine rheometer showed the influence of the material prehistory. The measurement with the injection molding machine rheometer led to a lower viscosity level compared to the capillary rheometer.