"In any manufacturing situation, we frequently see people working ahead. Instead of waiting, the worker works on the next job,... inventory begins to accumulate... This inventory has to be moved or neatly stacked. If these movements are regarded as 'work', soon we will be unable to tell waste from work... this phenomenon is called the waste of overproduction - our worst enemy - because it helps hide other wastes."
(p. 59, Ohno, T., 1988, Toyota Production System)
Material Flow Control (MFC) overcomes overproduction by addressing two important problems:
(i) whether a job should be released onto the shop floor; and,
(ii) whether a station should be authorized to produced.
Well-known pull approaches to MFC include: Kanban; Material Requirements Planning (MRP), Drum-Buffer-Rope (DBR), Constant Work-in-Process (ConWIP), Paired-cell Overlapping Loops of Cards with Authorization (POLCA), WorkLoad Control (WLC), Control of Balance by Card Based Navigation (COBACABANA) and Demand Driven MRP (DDMRP).
Both MFC decisions are typically accompanied by the decision regarding which job should be produced next. In the context of order release, this is typically referred to as backlog (or pool) sequencing and, in the context of station authorization, this is typically referred to as dispatching.
Studies on MFC typically take a location-based perspective of buffers. For example, the term “inventory” commonly refers to any flow item that does not move. This means it is associated to a location and the ‘dwell’ time at this location. Both perspectives can be taken when diagnosing inventory. Using the former location-based view, inventory is a count measure attached to a certain stock location. Using the latter item-centric perspective, inventory is a property of each individual flow item (e.g. its dwell time), which is attached to this flow item.
Using an item-centric perspective, the life-cycle information of products is digitally encapsulated at or on the products. This allows smart products easy access to information, which in turn allows for new forms of self-organized MFC. It is this item-centric MFC which is the main objective of this research group.
There are three main research streams:
Explore how the item-centric perspective changes existing theory on MFC, which is still entrenched in a location-based perspective.
Explore how digital twin can be used to facilitate item centric MFC “bottom-up” driven by smart products.
Explore how agent-based modelling can be used to facilitate the coordination of empowered smart objects.