Lot Sizes, Lead Times and In-Process Inventories

In many manufacturing problems, the total lead time taken to manufacture a product is an important consideration. Long lead times impose costs due to higher work-in-process inventory, increased uncertainty about requirements, larger safety stocks and poorer performance to due dates. Traditional lot sizing models ignore lead time related costs, although there are systematic relationships between lot sizes and lead times. This paper examines these relationships and their implications for lot sizing and work-in-process inventories, for batch manufacturing shops with queues.