Macro and micro-logistic aspects in defining the parts-feeding policy in mixed-model assembly systems

The handling activities within mixed-model assembly systems deal with two different logistic levels of the production environment. The micro-logistic level includes movements of parts across each assembly station due to pick to assembly activities. The macro-logistic level includes movements of parts within the supermarket and to deliver the stock-keeping units to the assembly stations. The most frequently adopted part-feeding policies, i.e., kanban system and kitting system, strongly influences both logistic levels with opposite effects. The former continuously refills the assembly stations; the latter prepares and delivers kits of components for each product. Moving from kanban to kitting system the time spent at the macro-logistic level increases. On the contrary, the time spent in part handling at the micro-logistic level decreases when moving from kanban to kitting system. Effective trade-offs are encouraged. This paper analyses the two introduced part-feeding policies, including hybrid possibilities, through an operative total handling time comparison model. The findings from five industrial cases belonging to different sectors and a global simulation analysis are discussed. Conclusions about the impact of some of the most important logistic variables of the production system to the whole performances drive the industrial practitioners in the part-feeding policy selection.