Lean diagnosis: eight wastes & value-stream maps

Before you speed anything up, find out where the time actually goes — it is almost never in the work.

The idea

Map the process before you change it. Draw every step from order to delivery, mark which steps actually add value the customer would pay for (VA) and which don’t (NVA), and measure two clocks: lead time (order in to order out) and touch time (the real work).

The gap between them is where the waste hides — usually as waiting. In most processes the item is worked on for minutes and waits for hours. Baseline that honestly and improvement becomes measurable instead of a hunch.

How it works

Two clocks and one ratio. Baseline them for the current state, then attack the biggest block of time — which is almost always the waiting between steps, not the steps themselves.

lead time  = clock time, order in to order out
touch time = actual work time = 40 min   (constant — the work doesn't change)
   value-adding (pick + pack)              = 18 min
   non-value  (log + approve + inspect)   = 22 min

waiting (batch of 10): each order waits while the rest of its batch is
                       processed at every station
   ~ (batch - 1) x touch = 9 x 40 = 360 min

lead time  = touch + waiting = 40 + 360 = 400 min
cycle efficiency = touch / lead = 40 / 400 = 10%

switch to one-piece flow (batch = 1):
   waiting -> 0    lead = 40 min    efficiency = 100%
   same work, delivered ~10x sooner — you deleted the waiting, not the work.

Notice what didn’t move: the 40 minutes of touch time. Speeding up the 10-minute pick step would have shaved a rounding error. Shrinking the batch cut the lead time tenfold.

The eight wastes (mnemonic DOWNTIME) — what to look for on the map:

• Defects — rework, scrap, corrections
• Overproduction — making more or sooner than needed
• Waiting — queues, approvals, idle time
• Non-utilised talent — unused skills and ideas
• Transportation — moving things around
• Inventory — work piled up between steps
• Motion — unnecessary movement of people
• Extra-processing — doing more than the customer needs

When to use it

Watch out for

• Speeding up a step that isn’t the constraint. Making a non-bottleneck faster just piles more inventory in front of the bottleneck. Fix flow, then the constraint.
• Reporting touch time as if it were lead time. Teams love to quote the 40 minutes of work; the customer feels the 400 minutes of clock. The gap is the opportunity, so measure both.
• Drawing the future state before the current state. You cannot improve what you never honestly baselined. Map what is, with real numbers, first.
• Mistaking busy for productive. Pushing every station to 100% utilisation guarantees queues. A little slack is what lets work flow.
• Deleting necessary non-value steps blindly. Some NVA (a regulatory check, a safety inspection) can be reduced but not removed. Separate pure waste from necessary NVA before you cut.

Worked example

An interviewer says: “Order-to-ship takes us five days, but there’s maybe 40 minutes of actual work in it. Where do you look?” A strong answer resists the urge to optimise a step. First, map the current state and measure lead time versus touch time — a cycle efficiency near 1% tells you the five days is almost entirely waiting. Then find the biggest queues: orders batched before shipping, an approval sitting in someone’s inbox, inventory stacked between stations. Attack those — smaller batches, one-piece flow, pulling approvals inline — and re-baseline to prove the lead time dropped. You explicitly do not start by buying a faster picking machine, because the picking was never where the time went.