Modeling arrival-to-departure sequence disorder in flow-controlled manufacturing systems

Flow control policies, such as clear the largest buffer first, have been used extensively in mediating server access between multiple job-arrival processes within manufacturing systems requiring significant set-up times between job types. Although the stability and performance characteristics of clearing policies have been studied, how these clearing policies affect the growth in arrival-to-departure sequence disorder across a machine or workcell is still an area for further research. In this paper, a closed-form model is formulated that characterises the steady-state average arrival-to-departure sequence disorder experienced by jobs processed through a stable flow controlled manufacturing system. Specifically addressed are the effects of upstream sequence disorder on the work-in-process of a downstream assembly process. A simulation study is used to validate the model’s accuracy and applicability in predicting steady-state average arrival-to-departure sequence disorder. A simulation study of an assembly process shows that by balancing upstream steady-state average sequence disorder, downstream work-in-process can be minimised while under a logical component grouping constraint.