The use of flowlines to simplify routing complexity in two-stage flowshops

Flexible manufacturing systems art: often designed as flowshops supported b y automated material handling devices that facilitate routing among any two processors of adjacent stages. This routing structure is complex, and resu lts in excessive capital investment and costs of management. In this paper we propose a decomposition of two-stage flowshops into smaller independent flowlines that allow for unidirectional routing only. We solve optimally th e problem of minimizing makespan on two parallel flowlines, by means of a D ynamic Programming algorithm (DP). Based on DP we develop lower bounds on t he throughput performance of environments that consist of more than two flo wlines. We present several heuristic algorithms and report their optimality gaps. Using these algorithms, we show that the decomposition of two stage flowshops with complicated routing into flowline-like designs with unidirec tional routing is associated with minor losses in throughput performance, a nd hence significant savings in material handling costs.