It is quite difficult to master the functioning of a rubber extruder, The difference in rheological behaviour from one batch of rubber to the other provokes functional changes. The latter are difficulties to master as they have very long delays, This study deals with the definition of a dynamic model which describes the behaviour of the extruder. First, a great number of parameters are recorded, The main perturbation is due to the viscosity which differs from one batch to the other. Secondly, a dynamic model describing the output (throughput) according to the setting (screw speed) and the perturbation (viscosity) is established.