Abstract.The design of a supply system for an assembly line possess many challenges. A tool that helps the decision making and the adjustment of the supply system parameters is the dynamic simulation. This article has the aim of showing on a given case, the road from workstation layout, to its simulation model and an example of parameter that can vary and its effect of workstation performance. Starting from the 3D model of the workstation, varying the number of diversities present in the workstation, by using the simulation we can see the effect of this variation on the workstation cycle time.