The formation of subfamilies for machine loading of flow-line cells

Cellular manufacturing constitutes a key element of contemporary approaches to manufacturing such as just-in-time and flexible manufacturing systems. In some settings, it may not be possible to release all members of a family to a cell at the same time due to tooling, level of the in-process inventory and limited machine buffer capacity constraints. When such constraints exist, one approach is to partition each family into subfamilies. In this research, the authors consider the effective partitioning of a family of parts into subfamilies in cyclically scheduled cells involving unidirectional material flow between machines laid out in a loop and where capacity constraints on tooling are present. The criterion for forming subfamilies is the minimization of the total machine idle time. This criterion maximizes the rate of output of the cell as well as maximizing machine utilization. A batching approach to part and tool change is utilized and all tool magazine set-ups are assumed to occur off-line while the cell is in operation. The authors present a model for the formation of subfamilies using the above criterion and develop four heuristic approaches based on it. They then examine their effectiveness by conducting computational experiments over a wide range of realistic situations generated by varying the characteristics of the operating environment, tooling requirements and tool magazine capacity.