Work out lead time estimate instantly with clear inputs, formula shown and shareable results.
Manufacturing lead time is the sum of process, queue, move and inspection time. In most job shops queue dominates, often accounting for 80-95% of elapsed time, which is why lead time falls dramatically when WIP is reduced even though nothing about the machining gets faster.
Lead time
Lead time = process + queue + move + inspection time
Value-added ratio
VA ratio % = process time x 100 / total lead time
Queue grows non-linearly with utilisation. At 90% machine loading, average queue is around nine times the process time; at 95% it is nineteen times. High utilisation and short lead time are in direct conflict.
Not from the customer's point of view — it is necessary waste. Building quality into the process so inspection can be reduced is a standard improvement route.