Balancing assembly lines with variable parallel workplaces: Problem definition, model and exact solution procedure

Assembly line balancing problems (ALBP) arise whenever an assembly line is con- figured, redesigned or adjusted. An ALBP consists of distributing the total workload for manu- facturing any unit of the products to be assembled among the work stations along the line sub- ject to a strict or average cycle time. Traditionally, stations are considered to be manned by one operator, respectively, or duplicated in form of identical parallel stations, each also manned by a single operator. In practice, this assumption is usually too restrictive. This is particularly true for large products like cars, trucks, busses and machines, which can be handled by several op- erators performing different tasks at the same time. Only restricted research has been done on such parallel workplaces within the same station though they have significant relevance in real- world assembly line settings.<BR> In this paper, we consider an extension of the basic ALBP to the case of flexible parallel work- places (VWALBP) as they typically occur in the automobile and other industries assembling large products. The problem is defined and modelled as an integer linear program. As a solution approach a branch-and-bound procedure is proposed which also can be applied as a heuristic. Finally, computational experiments documenting the solution capabilities of the procedure are reported.