The purpose of this study is to investigate due date setting procedures and dispatching decisions in a flow line cell with family setups. In this environment, setups are not required when switching from a job in a given family to a job in the same family. However, switching from a job in one family to a job in another family requires a setup. Family setups in this shop are sequence independent. The dispatching decisions in this shop are threefold: (1) when should the decision to switch from one part family to another be made; (2) once the decision to switch families is made, how should the next part family be chosen (next family decision); and (3) how should the jobs within a family be prioritized (next job decision)? If the decision to switch classes can only be made after the current family is exhausted, the rule is called a class exhaustion rule. Otherwise the rule is a truncated rule. The results indicate that the due date setting procedure has a major impact on how dispatching should be performed in the shop. The family exhaustion procedure using the APT next family rule and the SPT next job rule is the best performer for mean flow time. When setup times are long, the SEQ due date rule using the family exhaustion procedure with the FCFS next family and the EDD next job rules performed well for due date criteria. When setup times are short, the EDD/T, Sawicki truncation rule and the family exhaustion rules performed well for due date criteria.
Job batching is used extensively in manufacturing and the relevant theoretical considerations have been well‐researched. However, while batching is also employed in mass services, it is not clear to what extent the manufacturing theory may be transferred. A single case study of a court scheduling service system with imbedded instances of batching was studied to address this question. The findings and analysis of the case indicate that while the factors that affect batching in manufacturing still apply, so do additional factors. The net effect is a broader set of considerations which influence the determination of when batching is desired in mass services and how big batches should be. Definitions of these factors, their relationships with batch size, and testable hypotheses are offered.
The drum-buOE er-rope (D BR ) planning and control system is relatively new in the published literature. As such, many issues relating to various operating policies have yet to be resolved. In this paper, we look at three such policies. F irst we study selected order review/release (ORR ) methodologies that have appeared in the published literature to be used as the rope component in DBR . Secondly, we study the impact of lot splitting by breaking process batches into numerous transfer batches. Lastly, the impact of capacity balance between the bottleneck resource and non-bottleneck resources are modelled. A simulation model of an existing V plant that manufactures pliers is constructed. R esults indicate that the appropriate choice of each operating policy is a function of the shop performance criteria felt to be important by management. N o previous paper has studied the feasibility of using the various OR R methodologies in a D BR environment. We show that the performance of each is dependent on other conditions within the shop. Likewise, the impact of lot splitting has yet to be studied. We found that splitting process batches into smaller transfer batches nearly always improved shop performance criteria. F urther, simulation results indicate that shop inventory levels necessary to achieve comparable service levels is a function of the capacity balance between bottlenecks and non-bo ttlenecks, i.e. capacity slack. As capacity slack increases, thereby reducing capacity balance, shop inventory levels show a corresponding decrease.
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