Planning hybrid U-shaped assembly systems using heuristics and simulation

For small-volume products in particular, U-shaped assembly systems represent an important alternative to straight-line systems. For this kind of system, staff assignment can take various forms: assignment to adjacent and opposing stations, mixed and one-piece flow assignment. In this paper, a U-shaped assembly system is defined on the basis of a known method for balancing straight-line assemblies, and the most suitable form of staff assignment is then determined. If the station layout is interpreted as a capacity graph, and if staff assignment is defined in the form of a staff assignment graph, specific methods must be used to solve the staff assignment problem as those used to match the precedence and capacity graphs for the purpose of line balancing. It is shown that the performance of simulated solutions sometimes varies greatly from that of static balancing solutions, in particular if staff travel times are taken into account.