Lead Time

Cutting Manufacturing Lead Time Queue by Queue

In a typical shop, processing touches the part only 5 to 10 percent of the lead time; the rest is queue. This playbook measures the segments, caps WIP, and installs the release discipline that cuts lead time 25 to 40 percent.

Lead time is the number customers actually buy. Quote 15 days when competitors quote 8 and you lose the order; quote 8 and deliver in 15 and you lose the account. Internally, lead time is inventory: at $50,000 of WIP entering the floor daily, every day of lead time holds $50,000 of cash, so cutting 20 days to 12 releases $400,000 permanently. Little's Law makes the link exact: WIP equals throughput times lead time. And the uncomfortable industry fact is that in a typical job shop, actual processing touches the part only 5 to 10 percent of the lead time. The other 90 percent is queue, and queue is a management choice.

Measure it in segments or you cannot fix it: queue time, setup and run, inspection, and move or release time. Worked example on a machined housing: 6.5 days of queue across three work centers, 1.5 days of setup and run, 1 day waiting for and passing inspection, and 1 day of move and order release administration, 10 days total. The Manufacturing Lead Time calculator adds the segments; the insight is the ratio, 15 percent touch time and 85 percent waiting. Timestamp orders at each queue entry and exit for 30 orders and you have the pareto. Most plants discover one work center holds 50 to 60 percent of total queue, and that is the constraint wearing a name tag.

Benchmarks vary by mode: make-to-stock assembly should run 1 to 5 days, machined make-to-order 5 to 15, and engineered-to-order 4 to 12 weeks. More useful than absolutes is flow efficiency, touch time over total lead time: typical plants run 5 to 15 percent, good plants 25, and world-class cells exceed 40. Track lead time variability too, because customers plan around the 90th percentile, not your average: a shop averaging 10 days with a 90th percentile of 22 gets treated as a 22 day supplier. Quoted versus actual should match within 10 percent; a plant quoting 12 days and averaging 17 is teaching customers to inflate every order.

Queue is the target, so the levers are queue levers. Release control first: launching orders early does not finish them early, it just lengthens every queue; hold releases until the constraint has capacity, and WIP drops 20 to 40 percent with zero capital. Cut lot sizes: halving a lot roughly halves its queue and run contribution to lead time at the same utilization. Attack setup so small lots stay economic; a 90 minute setup cut to 25 changes the lot-size math completely. Overlap operations by moving partial lots ahead. And pull inspection to the line: an inspection queue of 1 day on every order is 1 day of lead time bought back by a $70,000 inspector reallocation.

Failure modes: expedite culture, where 30 percent of orders wear hot tags, which reshuffles queues, adds setups, and lengthens average lead time for everyone; cap expedites at 5 percent of orders with plant manager sign-off. Batch releasing on Mondays creates a weekly WIP wave and a Friday inspection pile-up; release daily. Measuring only shipped orders hides the 15 stuck orders aging in a rework loop; run a weekly aging report of every order past 1.5 times standard lead time. And loading to 95 percent utilization while promising short lead times: queueing math says wait times roughly double between 85 and 93 percent utilization, so pick one promise.

The cadence: daily, review orders past due or aging beyond 1.5 times standard, and clear release decisions against constraint capacity, 15 minutes. Weekly: lead time by segment for completed orders, the flow efficiency trend, WIP count versus a stated cap, and one queue-reduction action per work center owner. Monthly: recalculate standard lead times from actuals, because quoting from 2 year old standards is how sales sells capacity you do not have; review the 90th percentile against the quote. Quarterly: value stream map the top product family, retime the segments, and reset the WIP cap. Expect 25 to 40 percent lead time reduction in year one, mostly from release discipline, before spending anything.

World-class flow: lead times 50 to 70 percent below industry peers, flow efficiency above 35 percent, a 90th percentile within 20 percent of the mean, quoted dates hit 98 percent of the time, and WIP capped and visible on a board the plant manager walks daily. Orders release one day's worth at a time against constraint capacity. Inspection happens in-line within the hour. Expedites are rare enough that the whole plant notices one. Sales quotes lead time from a system fed by last month's actuals, and the plant treats a lead time increase like a safety incident: investigated within 24 hours, root cause named, countermeasure owned.

Published 2026-07-02.