How much of lead time is adding value. Usually under 10 percent.
Process cycle efficiency is the metric that explains why lead times feel so much longer than they should. On a value stream where the actual cutting and assembling adds up to less than a day of work, finished parts can still take a week to ship. The math says it should not. The reality says it does. PCE captures the difference, usually with a number that shocks people the first time they see it. Five percent is common. Two percent is not unusual. Anything above ten percent is impressive in a non-continuous-flow environment.
"If only 5 percent of lead time is value-added, 95 percent is opportunity."
The calculation is value-added time divided by total lead time, both measured for the same product through the same process. The arithmetic is easy. The classification is where the discipline lives.
The customer's willingness to pay is the standard test. A step is value-added if all three are true:
Everything else is non-value-added: transport between operations, queuing between steps, inspection, retrieval from storage, setup, paperwork, and the universal waiting that fills the gaps between productive activities. In most shops, non-value-added time dominates lead time so thoroughly that the math feels wrong the first time it is calculated. The math is right. The lead time is largely waiting.
Imagine a 25-person CNC machine shop quoting parts with a four-week lead time. A new customer asks why the lead time is so long when the part takes 90 minutes of actual machining. The owner does not have a clean answer. A value stream mapping exercise produces one.
The total lead time of 28 days breaks down roughly as follows: 8 days waiting for raw material to release from the supplier, 1 day in receiving inspection, 6 days in queue at the main mill, 90 minutes of actual machining, 4 days in queue at the lathe, 45 minutes of actual lathe work, 5 days in queue at deburr and inspection, 30 minutes of actual deburr and inspection, 3 days waiting in finished goods for the truck. Value-added time totals 2 hours and 45 minutes against 28 days. PCE is about 0.4 percent.
The shop is not slow. The machining is fast. The lead time is consumed almost entirely by waiting. The improvement project that follows targets the largest queues first: weekly raw material releases with the supplier, kanban between mill and lathe, finished-goods scheduled pickups. None of this changes the actual machining time. PCE climbs from 0.4 to 1.5 percent and lead time drops from 28 days to 8. The customer asks for a quote on a bigger contract. The math worked.
Process cycle efficiency is identical in calculation to value-added ratio. It is anchored in the broader value/non-value distinction captured by value-added activity and non-value-added activity. It is closely tied to lead time and throughput time, since the denominator is total time through the stream. PCE belongs in any serious value stream mapping exercise.
The questions we hear most about this term.
Long-form guides that pick up where this definition leaves off, written for manufacturers running Arda today.
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