THE COST OF ELIMINATING EXCEPTIONAL ELEMENTS IN GROUP TECHNOLOGY CELL-FORMATION

Many researchers have suggested methods for the formation of machine cells/part families in group technology. However, few of these methods have addressed the possible existence of exceptional elements (EE) in a reasonable manner. EE can be the result of bottleneck machines whose processing is needed by parts assigned to more than one part family. They can also be caused by parts that require processing on machines assigned to more than one machine cell. The existence of EE in cell formation solutions is a nontrivial problem that requires interaction between machine cells intended to be independent for production efficiency. This paper presents a systematic method for identifying opportunities for reducing the number of intercell transfers caused by the existence of EE. The method recognizes how each EE in a cell formation solution may be involved in the creation of intercell transfers. The sequence of operation in each part routeing is also considered. The method then analyses the costs associated with alternative actions for the removal of the EE. The result is a prioritized list (based on relative cost-effectiveness) of the EE-removal actions. The method recognizes that interdependencies exist among EE: actions taken to eliminate one EE may have an effect on others as well. The process is demonstrated with an example.