Lean, made visible

Every 3½ minutes,
a car reaches Tomás.
He is drowning.

Three stations down, another worker stands idle. Same line, same pace — wildly different loads. A Yamazumi chart makes the imbalance impossible to ignore. Scroll to watch one balance itself.

MethodYamazumi
SettingEV Final Assembly
ZoneZone 3 · Stn 7
Takt210 s
01
Rear-Right
Rear-Left
Front-Right
Front-Left
Waste inside elements
Station 7 · Tomás R.
One operator,
231 seconds of work.
21 s over takt — every cycle
Time Observation · Station 7 · Tomás R.10 cycles · seconds
Work element12345678910LRT
Align rear drive unit6062586160636059616260
Torque 8 rear bolts4749484750474851494847
Retrieve connector · FL rack2219241921231920252219
Connect HV cable3941404239384039414339
Verify thermal sensor2425262427242526242824
Reset torque tool + scan4255444260474250455842
The lowest repeatable time isn't the lowest time. Cycle 3 hit 58 once — a one-off you can't bank on; the lowest time that repeats is the honest building block: 60 s. Rows 3 & 6 swing wildly — that's the job fighting back: a part that won't seat, a missing component, a quality issue. Real problems, not a faster operator.
Align drive · RR
Torque bolts · RR
Retrieve · FL
Connect HV · RL
Verify · RR
Reset + scan · RR
Station 7 · Tomás
231 s · 21 over takt
A clean job flows one way across the unit — front to back, so a moving line carries the operator along. Tomás's path jumps instead: rear-right, out to front-left, back to rear-left. Every jump against the flow is a walk — chasing the vehicle.
Stn 4
152s
Stn 5
188s
Stn 6
165s
Stn 7
231s
Stn 8
122s
Stn 9
122s
Operator A
~90% of takt
Operator B
~90% of takt
Operator C
~90% of takt
Operator D
~90% of takt
Operator E
next kaizen target
TAKT · 210 s
LOADED · ~90%
buffer
Σ cycle time 800 s ÷ takt 210 s = 3.81 → round up
Theoretical minimum: 4 operators
was 5 before waste removal · staffed today: 6
▲ Station 7 — over takt
Stations 8 & 9 sit idle ▾
▾ The red is waste — hiding inside the work
Four near takt · the 5th is the next kaizen target
The feeling everyone knows

Your station is packed. The one beside you breathes easy.

Tomás has 210 seconds to align a drive unit, torque eight bolts, run a high-voltage cable, and verify a sensor. He is the best tech in the zone — and still not fast enough. His lead, Marcus, has known for months. He just couldn't prove it.

Step 1 · Observe — 10 cycles

A clipboard, a stopwatch, ten cycles.

No spreadsheet. Dana times every distinct element Tomás performs — across ten cycles, because no two run the same. Engineered standards say what a task should take; the stopwatch at the gemba says what it does. Capture it on a Time Observation Sheet — our free one does the timing math for you.

cycles timed10
elements6
Step 2 · Lowest repeatable time

Not the fastest. The lowest time that repeats.

Don't grab the single quickest number — a 58 that happened once is a fluke you can't bank on. Take the lowest time the operator hits consistently. And never average: when an element swings wildly (rows 3 & 6), that fluctuation is the job fighting back — a part that won't seat, a missing component, a quality issue. Average it and you bury those problems inside the standard.

Step 3 · Stack by zone

Color each element by where it touches the unit.

This is the move that makes a Yamazumi more than a bar chart. Color by unit zonerear-right, rear-left, front-left. The goal isn't to pin someone to one zone — it's flow: start at the front and work back, and a moving line moves with you. When the colors jump around — front, back, front — that's walking, chasing the vehicle.

Step 4 · The red line

Takt: the pace demand sets.

435 productive minutes ÷ 124 vehicles = 210 seconds. Drop the line across the bar and the verdict is instant: Tomás stands at 231 s — 21 seconds over. This one job, on its own, cannot keep up.

Tomás231s
takt210s
over+21s
Step 5 · Line them up

Six operators. One skyline.

Every station in Zone 3, side by side, against the same takt line. Station 7 spills over; Stations 8 and 9 sit idle. The imbalance you could only feel is now a shape on a wall — and the total work content is 980 seconds across six people.

operators6
work content980s
Step 6 · Don't move work — improve it

Waste isn't a block. It hides inside the work.

The reflex is to shove tasks from the full station to the empty one. Wrong first move. X-ray each element and the waste appears as a fraction within it — the walk buried in “retrieve connector,” the wait inside “reset tool.” Improve the element; don't relocate it.

Step 7 · Strip the waste

180 seconds of the easy waste, gone.

Move the Front-Left rack so the walk vanishes. Fix the torque fault so the wait disappears. The spread-out waste — the walks, the tool waits — comes off first: about 180 seconds across the line. Work content drops from 980 to 800, and every bar sits under takt. No one was asked to hurry.

waste cut180s
work left800s
Step 8 · Sigma cycle time

How many operators do you actually need?

Add up all the real work and divide by takt: Σ 800 s ÷ 210 s = 3.81, round up to 4. The honest floor was hiding in plain sight — the line is staffed with six. That's two operators of opportunity, visible before a single change hits the floor.

need4
staffed6
opportunity2
Step 9 · Rebalance to ~90%

Now — and only now — move work.

With the easy waste gone, redistribute the elements into jobs loaded to about 90% of takt — not 100%, so a jam or a quality check doesn't stop the line. But elements are indivisible: you can't pour 800 seconds into four even buckets. You land at five — four jobs near takt, and a fifth holding the leftover that wouldn't fit.

The result

The line breathes — and points at what's next.

Six lopsided stations became five honest ones: four loaded near takt, and a fifth holding the isolated leftover. Tomás reaches without stepping; nobody drowns, nobody waits. And that underloaded fifth isn't a failure — it's the next kaizen target, made obvious. Absorb its work into the others and you reach the theoretical four. Six → five today → four next.

And it gives everyone a single picture of reality — no more “I think” or “it feels like.” Here's what's actually happening. That shared picture is what turns a room of opinions into alignment — and a team that can go fix it together.

Now build your own

You've seen it. Now stack your line.

The free Yamazumi builder — drop in your elements, color them by zone, draw your takt line, and watch the theoretical operator count update as you rebalance. No spreadsheet, no login.

Good to know

Frequently asked

What is a Yamazumi chart?
An operator (or work) balance chart that stacks each person's work content side by side against takt time, so you can see overburden, idle time, and waste across a whole line in one picture.
How is it different from a cycle-time bar chart?
A plain bar chart tells you who is overloaded. Coloring each element by unit zone tells you why — layout mismatches and walking that a raw cycle-time number hides entirely.
How many operators do I actually need?
Add up the real work content across the line and divide by takt time (Σ ÷ takt), then round up. That theoretical minimum is frequently one or two fewer than the line is staffed for.
Why not load operators to 100% of takt?
Because real shifts have jams, missing parts, and quality checks. Loading to about 90% leaves a buffer so the first small problem does not stop the line — while still avoiding paid-for idle time.
MS
Matthew Savas

Founder of Kaizumi, an AI-powered Lean training platform. More about Matthew →

Updated June 9, 2026 · Drafted with AI assistance and reviewed by Matthew Savas for accuracy.