Robust versus stable layout design in stochastic environments

This paper discusses the problem of the layout flexibility problem. In an environment affected by stochastic product flows, identifying the optimal layout acquires particular relevance, as the layout itself must behave efficiently under varying conditions and levels of item production. This work advocates the need for modifying the parameters usually proposed in literature to optimize the physical location of the workstations on the shopfloor. These parameters will consider not only the average value of the part flows between two generic machines, but also the standard deviation of the flows themselves. With such quantities, it is possible to design layouts which guarantee a more regular performance, in terms of material handling requests when volumes and demand mix change over time (market dynamics). Therefore, this study concerns the formulation of stability layout indices which are based on the flow distributions between each machine pair (i.e. as a function of the route-sheets and the demand distribution of each product processed in the manufacturing system). These indices allow the analyst to calculate the risk of deterioration in the layout performances due to market dynamics.