Unique control priorities for parallel machines in high-variety manufacturing

Previous literature on high-variety manufacturing developed various control policies that include a ‘shift mechanism’ that changes the control priority during periods of low and peak demand. Embedded in priority rules or release methods, this shift mechanism is developed in a setting with a single capacity source, making the need to shift between control priorities necessary. However, when there are multiple capacity sources – for example, by identical parallel machines – we can use a ‘dual focus mechanism’, where each capacity source can have its unique control priority, regardless of demand levels. Using discrete event simulation, we find that the combination of shift and focus mechanisms leads to the best average performance. But this is at the expense of an extreme delay for orders with large process times, which can be prevented by a control policy that uses a dual focus mechanism only, whilst still realising competitive average performance.