Leadtime is the measure of time between the workorder hitting the shop floor and the completion of the product (ready to ship).
This time is composed of two items (operational time and inoperational time)
The operational time is required to produce the item, the inoperational time is not required (queuing, breakdown of equipment, waiting for employees).
While some queuing might be necessary it is estimated that 75-95% of all nonproductive delay result form unplanned queueing… the item produced before is not ready.