Manufacturing Lead Time. The amount of time each unit spends in the manufacturing process (sometimes called Throughput Time). This includes time spent actively being worked upon at each step of the process as well as any time spend waiting between steps. The concept of a lead time applies to the total time spent in any process in which the start and finish are well-defined events. We can talk about lead times, for example, in service operations, or in the entire order-to-delivery process.